Tuesday 7 May 2013

COMPUTER GRAPHICS QUESTION BANK

UNIT – I
PART – A
1     Define Computer graphics.
             Computer graphics remains one of the most existing and rapidly growing
computer fields. Computer graphics may be defined as a pictorial representation or graphical representation of objects in a computer
2    What is meant by scan code?
              When a key is pressed on the keyboard, the keyboard controller places a code carry to the key pressed into a part of the memory called as the keyboard buffer. This code is called as the scan code.
3    What is meant by refreshing of the screen?
            Some method is needed for maintaining the picture on the screen. Refreshing of screen is done by keeping the phosphorus glowing to redraw the picture repeatedly. (i.e.)By quickly directing the electronic beam back to the same points.
4     Define Random scan/Raster scan displays?
             Random scan is a method in which the display is made by the electronic beam which is directed only to the points or part of the screen where the picture is to be drawn. The Raster scan system is a scanning technique in which the electrons sweep from top to bottom and from left to right. The intensity is turned on or off to light and unlight the pixel.
5     List out the merits and demerits of Penetration techniques?
             The merits and demerits of the Penetration techniques are as follows
             • It is an inexpensive technique
             • It has only four colors
             • The quality of the picture is not good when it is compared to other
               techniques
             • It can display color scans in monitors
     • Poor limitation etc.
6     List out the merits and demerits of DVST?
         The merits and demerits of direct view storage tubes [DVST] are as follows
         • It has a flat screen
         • Refreshing of screen is not required
         • Selective or part erasing of screen is not possible
7    What do you mean by emissive and non-emissive displays?
          The emissive display converts electrical energy into light energy. The plasma panels, thin film electro-luminescent displays are the examples.
The Non emissive are optical effects to convert the sunlight or light from any other source to graphic form. Liquid crystal display is an example.
8    List out the merits and demerits of Plasma panel display?
Merits:
           • Refreshing is not required
           • Produce a very steady image free of Flicker
           • Less bulky than a CRT.

         Demerits:
        • Poor resolution of up to 60 d.p.i
        • It requires complex addressing and wiring
        • It is costlier than CRT.
9    What is persistence?
                 The time it takes the emitted light from the screen to decay one tenth of its original intensity is called as persistence.
10    What is resolution?
               The maximum number of points that can be displayed without an overlap on a CRT is called as resolution.
11    What is Aspect ratio?
              The ratio of vertical points to the horizontal points necessary to produce length of lines in both directions of the screen is called the Aspect ratio. Usually the aspect ratio is ¾.
12    What is meant by Addressability?
              The Addressability is the number of individual dots per inch (d.p.i) that can be\ created. If the address of the current dot is (x, y) then the next dot will be (x+y), (x+y+1) etc.
13    What is a dot size?
               Dot size may be defined as the diameter of a single dot on the devices output. Dot size is also called as the Spot size.
14    What is interdot distance?
              Interdot distance is the reciprocal of addressability. If the addressability is large, the interdot distance will be less. The interdot distance should be less to get smooth shapes
15    What is the difference between impact and non-impact printers?
             Impact printer press formed character faces against an inked ribbon on to the paper. A line printer and dot-matrix printer are examples. Non-impact printer and plotters use Laser techniques, inkjet sprays, Xerographic process, electrostatic methods and electro thermal methods to get images onto the papers. Examples are: Inkjet/Laser printers.
16    What are the features of Inkjet printers?
               • They can print 2 to 4 pages/minutes.
               • Resolution is about 360d.p.i. Therefore better print quality is achieved.
               • The operating cost is very low. The only part that requires replacement  
                 is ink  cartridge.
               • 4 colors cyane, yellow, majenta, black are available.
18    What are the advantages of electrostatic plotters?
             • They are faster than pen plotters and very high quality printers.
             • Recent electrostatic plotters include a scan-conversion capability.
             • Color electrostatic plotters are available. They make multiple passes  
               over the paper to plot color pictures.
19    Define pixel?
              Pixel is shortened forms of picture element. Each screen point is referred to as pixel or pel.
20    What is frame buffer?
             Picture definition is stored in a memory area called frame buffer or refresh
buffer.
21    What is bitmap and what is pixmap?
              The frame buffer used in the black and white system is known as bitmap which take one bit per pixel. For systems with multiple bits per pixel, the frame buffer is often referred to as a pixmap.
22    What is a Vector display or stroke writing or calligraphic display?
             Random scan monitors draw a picture one line at a time and for this reason are also referred as vector displays.
23    Where the video controller is used?
             A special purpose processor, which is used to control the operation of the display device, is known as video controller or display controller.
24    What do you mean by scan conversion?
            A major task of the display processor is digitizing a picture definition given in an application program into a set of pixel-intensity values for storage in the frame buffer. This digitization process is called scan conversion.
25    What is Run length encoding?
            Run length encoding is a compression technique used to store the intensity values in the frame buffer, which stores each scan line as a set of integer pairs. One number each pair indicates an intensity value, and second number specifies the number of adjacent pixels on the scan line that are to have that intensity value.
26    What is an output primitive?
         Graphics programming packages provide function to describe a scene in terms of these basic geometric structures, referred to as output primitives.
27    What do you mean by ‘jaggies’?
       Line with stair step appearance is known as jaggies.
28    Distinguish between convex and concave polygons?
       If the line joining any two points in the polygon lies completely inside the polygon then, they are known as convex polygons. If the line joining any two points in the polygon lies outside the polygon then, they are known as concave polygons.
29    What is seed fill?
       One way to fill a polygon is to start from a given point (seed) known to be inside the polygon and highlight outward from this point i.e neighboring pixels until encounter the boundary pixels, this approach is called seed fill.
30    What is scan line algorithm?
       One way to fill the polygon is to apply the inside test. i.e to check whether the pixel is inside the polygon or outside the polygon and then highlight the pixel which lie inside the polygon. This approach is known as scan-line algorithm.

31    What is a winding number?
      Winding number method is used to check whether a given point is inside or outside the polygon. In this method give a direction number to all the edges which cross thescan line. If the edge starts below the line and ends above scan line give direction as -1 .otherwise1. Fr polygons or two dimensional objects, the point is said to be inside when the value of winding number is nonzero.
32    What is tiling patterns?
The process of filling an area with rectangular pattern is called tiling and
rectangular fill patterns are sometimes referred to as tiling patterns.
33    What is aliasing?
In the line drawing algorithms, all rasterzed locations do not match with the true
line and have to represent a straight line. This problem is severe in low resolution
screens. In such screens line appears like a stair-step. This effect is known as aliasing.
34    What is anti aliasing?
The process of adjusting intensities of the pixels along the line to minimize the
effect of aliasing is called ant aliasing.
35    What is the purpose of presentation graphics?
    Presentation graphics is used to produce illustrations for reports or to generate 35- mm slides or transparencies for use with projectors.Presentation graphics is commonly used to summarize financial, statical,mathematical, scientific, and economic data for research reports ,managerial reports, consumer information bulletins, and other types of reports.
36    Define refresh buffer/frame buffer.
    The memory area where in picture definition is stored is called Refresh buffer. This memory area holds the set of intensity values for all the screen points. On a black and white system with one bit per pixel, the frame buffer is called a bitmap.
37    What is DDA?
    The Digital Differential Analyzer is a scan-conversion line algorithm based on calculating either difference in y-coordinate (dy) or difference in x-coordinate. We sample the line at unit intervals in one coordinate and determine corresponding integer values nearest the line path for the other coordinate.
38     What are the disadvantages of DDA algorithm?
• Round-off error in successive additions of the floating-point increment can cause the calculated pixel positions to drift away from the true line path for long line segments. • Rounding operations and floating-point arithmetic in procedure are still timeconsuming.
39     What is attribute parameter?
Any parameter that affects the way a primitive is to be displayed is referred to as an attribute parameter.
40    What are the basic line attributes?
Basic attributes of a straight line segment are its type, its width, and its color

PART – B

1     Explain Cathode Ray tube
2    Explain color CRT monitors
3    Explain direct view storage tubes
4    Explain Raster scan systems
5    Explain Random Scan System
6    Explain in detail about the DDA scan conversion algorithm
7    Explain Bresenhams line drawing algorithm
8    Explain Midpoint Circle algorithm
9    Explain Bresenham Ellipse generating Algorithm
10    Explain Boundary fill Algorithm
11    Explain Cohen Sutherland line clipping algorithm.
12    Explain Cyrus Beck line clipping algorithm.
13    Explain bout video controller
14    Explain about liquid crystal displays
15    What is seedfill algothm? Explain
16    Explain about scanline algorithm.


UNIT – II

PART – A
1    What is Transformation?
Transformation is the process of introducing changes in the shape size and
orientation of the object using scaling rotation reflection shearing & translation etc.
2    What is translation?
Translation is the process of changing the position of an object in a straight-line
path from one coordinate location to another. Every point (x , y) in the object must
under go a displacement to (x’,y’). the transformation is:
x’ = x + tx ; y’= y+ty
3    What is rotation?
A 2-D rotation is done by repositioning the coordinates along a circular path, in
the x-y plane by making an angle with the axes.
The transformation is given by: X’ = rcos (q + f) and Y|’= r sin (q + f).
4    What is scaling?
The scaling transformations changes the shape of an object and can be carried out by multiplying each vertex (x,y) by scaling factor Sx,Sy where Sx is the scaling factor of x and Sy is the scaling factor of y.
5    What is shearing?
The shearing transformation actually slants the object along the X direction or the
Y direction as required.ie; this transformation slants the shape of an object along a required plane.
6    What is reflection?
The reflection is actually the transformation that produces a mirror image of an
object. For this use some angles and lines of reflection.
7    Distinguish between window port & view port?
A portion of a picture that is to be displayed by a window is known as window
port. The display area of the part selected or the form in which the selected part is
viewed is known as view port.
8    What is the need of homogeneous coordinates?
To perform more than one transformation at a time, use homogeneous coordinates or matrixes. They reduce unwanted calculations intermediate steps saves time and memory and produce a sequence of transformations.
9    Distinguish between uniform scaling and differential scaling?
When the scaling factors sx and sy are assigned to the same value, a uniform
scaling is produced that maintains relative object proportions. Unequal values for sx and sy result in a differential scaling that is often used in design application.
10    What is fixed point scaling?
The location of a scaled object can be controlled by a position called the fixed
point that is to remain unchanged after the scaling transformation
11    Define Affine transformation?
A coordinate transformation of the form
X= axxx + axyy + bx , y ’ ayxx + ayy y +by
is called a two-dimensional affine transformation. Each of the transformed
coordinates x ‘ and y ‘ is a linear function of the original coordinates x and y , and
parameters aij and bk are constants determined by the transformation type.
12    Distinguish between bitBlt and pixBlt?
            Raster functions that manipulate rectangular pixel arrays are generally referred to as raster ops. Moving a block of pixels from one location to another is also called a block transfer of pixel values. On a bilevel system, this operation is called a bitBlt (bit-block transfer), on multilevel system t is called pixBlt.
13    List out the various Text clipping?
           All or none string clipping if all of the string is inside a clip window, keep it
otherwise discards. All or none character clipping discard only those characters that are not completely inside the window. Any character that either overlaps or is outside a window boundary is clipped. Individual characters if an individual character overlaps a clip window boundary, clip off the parts of the character that are outside the window.
14    Define Clipping.
Any procedure that identifies those portions of a picture that are either inside or outside of a specified region of space is referred to as a clipping algorithm or simply clipping. The region against which an object is clipped is called a clip window.
15    Define Window.
 A world-coordinate area selected for display is called a window.
16    Define view port.
An area on a display device to which a window is mapped is called a view port.
17    What is viewing transformation?
The mapping of a part of a world-coordinate scene to device coordinates is referred to as viewing transformation.
18    What are the types of Clipping?
• Point clipping
• Line clipping
• Area clipping
• Curve clipping
• Text clipping
19    What do you mean by view plane?
A view plane is nothing but the film plane in camera which is positioned
and oriented for a particular shot of the scene.
20    Define coherence properties?
A coherence property of a scene is apart of a scene by which relate one part of the scene with the other parts of the scene.

PART – B

1    Explain reflection and shear in 2D transformation?
2    Explain translation, Rotation and Scaling in 2D transformation?
3    Prove that successive 2D Scaling are Commutative.
4    Explain window to viewport transformation?
5    Give the 3x3 homogeneous transformation matrix for each of the following transformation sequence
i)    Rotate counter clockwise about the origin by 450 and then scale the x-direction by one half as large
ii)    Scale the y-direction by twice as tall ,shift down by 1 unit and then rotate clockwise by 300
6    Prove that 2D rotation and scaling commute if Sx=Sy or ө=nπ for integral n and that otherwise they do not.
7    Explain about Homogeneous co-ordinate transformation?
8    Prove that Successive 2D Translations are additive
9    Prove that Successive 2D Rotations are multiplicative
10    Prove that Successive 2D Scaling are multiplicative


UNIT – III
PART – A
1    What are the various representation schemes used in three dimensional objects?
Boundary representation (B-res) describe the 3 dimensional object as a set of
surfaces that separate the object interior from the environment.
Space portioning representation – describe interior properties, by partitioning the
spatial region containing an object into a set of small, no overlapping, contiguous
solids.
2    What Boundary representation?
It describes a 3D object as a set of surfaces that separate the object interior from the environment. e.g. polygon facets and spline patches.
3    What space-partitioning representation?
This is used to describe interior properties, by partitioning the spatial region containing an object in to a set of small, non-overlapping, contiguous solids. e.g.octree.
4    What is projection?
The process of displaying 3D objects on a 2D display is called as Projection
5    What are the types of projection?
• Perspective projection
• Parallel projection
6    What is parallel projection?
 In a parallel projection, coordinate positions are transformed to the view plane along parallel lines
7    What is Perspective projection?
 For a perspective projection object positions are transformed to the view plane along lines that converge to a point called the projection reference point.
8    What are the steps involved in 3D transformation?
• Modeling Transformation
• Viewing Transformation
• Projection Transformation
   Workstation Transformation
9    What do you mean by view plane?
A view plane is nothing but the film plane in camera which is positioned
and oriented for a particular shot of the scene.
10    What do you mean by Perspective projection?
Perspective projection is one in which the lines of projection are not
parallel. Instead, they all converge at a single point called the center of projection.
11    What is Projection reference point?
In Perspective projection, the lines of projection are not parallel. Instead,
they all converge at a single point called Projection reference point.
12    What are the different types of parallel projections?
The parallel projections are basically categorized into two types,
depending on the relation between the direction of projection and the normal to the
view plane. They are orthographic parallel projection and oblique projection.
13    What is orthographic parallel projection?
When the direction of the projection is normal (perpendicular) to the view
plane then the projection is known as orthographic parallel projection
14    What is orthographic oblique projection?
When the direction of the projection is not normal (not perpendicular) to
the view plane then the projection is known as oblique projection.
15    What is an axonometric orthographic projection?
The orthographic projection can display more than one face of an object.
Such an orthographic projection is called axonometric orthographic projection.
16    What is cavalier projection?
The cavalier projection is one type of oblique projection, in which the
direction of projection makes a 45-degree angle with the view plane.
18    What is cabinet projection?
The cabinet projection is one type of oblique projection, in which the
direction of projection makes a n angle of arctan (2)=63.4- with the view plane.
19    What is vanishing point?
The perspective projections of any set of parallel lines that are not parallel
to the projection plane converge to appoint known as vanishing point.
20    What do you mean by principle vanishing point?
The vanishing point of any set of lines that are parallel to one of the three
principle axes of an object is referred to as a principle vanishing point or axis
vanishing point.
21    What is view reference point?
The view reference point is the center of the viewing coordinate system. It
is often chosen to be close to or on the surface of the some object in the scene.
22    List out the 3D Issues?
More Complicated Objects than 2D
More involved geometric transformations
Viewing transformations much more complicated
Projection onto a two dimensional output display (usually)
Identification of Visible Surfaces

PART – B

1    Give the 3-D transformation matrix for
    Translation
    Scaling
    Rotation
    Reflection
    Shearing
2    Drive the transformation matrix for rotation about an arbitrary axis
3    Drive the transformation matrix for rotation about an arbitrary Plane
4    Drive the transformation matrix for reflection about an given plane
5    Explain 3-D Viewing transformation
6    Explain Orthographic projection
7    Explain the types of Perspective Projection
8    Explain 3-D clipping
9    Explain Oblique projection
10    Prove that Successive 3D Translations are additive
11    Prove that Successive 3D Rotations are multiplicative
12    Prove that Successive 3D Scaling are multiplicative
13    Prove that successive 3D Scaling are Commutative.


UNIT – IV

PART – A
1    What is solid modeling?
               The construction of 3-dimentional objects for graphics display is often referred to as solid modeling.
2    List the properties of good modeling or representation
    Domain
    Unambiguity
    Uniqueness
    Accuracy
    Validness
    Closure
    Compactness and Efficiency
3    What do you mean by boundary points?
             The points whose distance from the object and the object’s complement is zero are called boundary points. They need not be a part of the object.
4    What is close set and open set?
               A closed set contains all its boundary points, whereas an open set contains none.
5    List some solid representation methods.
    The solid representation methods are
    Wireframe model
    Sweep representations
    Spatial Partitioning representations
    Octree representation
    Boundary Representation (B-rep)
    Constructive solid geometry(CSG)
6    What is wireframe model?
        A wireframe model consists of two tables, the vertex table and the edge table.Each entry of the vertex table records a vertex and its co-ordinate values, while each entry of the edge has two components giving the two incident vertices of the edge.
7    What are Blobby objects?
       Some objects do not contain the fixed shape but change their surface characteristics in certain motions or when proximity to other objects.These object can be described as exhibiting “blobbiness” and are often simply referred to as blobby objects,since their shapes show a certain degree of fluidity 
8    What is translational sweep and rotational sweep?
       The sweep in which the 2D shape is swept along a linear path normal to the plane of the area to construct the 3D object is translational sweep.The sweep in which the 2D shape is rotated about an axis of rotation specified in the plane of 2
D shape to produce the 3D object is rotational sweep
9    What is voxels?
          Spatial-occupancy enumeration is a special case of cell decomposition in which the object is decomposed into identical cells arranged in a fixed, regular grid . These cells are often called voxels(volume elements)
10    What is cuberille?
        The most common common cell type is the cube and the representation of space as a regular array of cubes is called a cuberille.
11    What is constructive solid geometry(CSG)?
        The technique for solid modeling used to combine the volumes occupied by overlapping 3-D objects using Boolean set operations is called constructive solid germetry(CSG)
12    What is use of hidden line elimination removing algorithm?
          The hidden line removal algorithm determines the lines, edges, surfaces or volume that are visible or invisible to an observer located at a specific point in space.
13    What are the four possibilities of the surface can have with a specified area boundary?
1.surrounding surface
2.Overlapping surface
3.Inside surface
4.Outside surface
14    What are the basic functions of depth soring method?
    Surface are stored in order of decreasing depth
    Surface are scan converted in order, starting with the surface of greatest depth
15    What is a BSP tree?
        A binary space-partitioning (BSP) tree is an efficient method for determining object visibility by painting surfaces onto the screen from back to front, as in the painter’s algorithm. The BSP tree is particularly useful when the view reference point changes, but the objects in a scene are at fixed positions.
16    What do you mean by back face removal?
         The back face removal is an algorithm by which we can identity all the back surfaces of an object and display only the boundaries for visible surfaces.
17    List the methods used for hidden surface elimination based on area subdivision algorithm.
1.Warnock’s Algorithm
2.A-buffer Algorithm
3.Weiler-Atherton Algorithm
18    What is stored in the surface field of A-buffer algorithm?
    Surface identifier
    Depth
    RGB intensity
    Opacity parameter
    Percentage of area coverage
    Other surface rendering parameters
19    Define Octrees?
            Hierarchical tree structures called octrees, are used to represent solid objects in some graphics systems. Medical imaging and other applications that require displays of object cross sections commonly use octree representation
20    Name any two 3D graphics package procedures related with visible surface detection
1.BackFace
2.DepthBuffer


PART – B

1    Explain Octree Representation
2    Explain Boundary Representation (B-reps)
3    Explain Solid Geometry (CSG)
4    Explain Wireframe models
5    Explain Back-Face Detection
6    Explain Z-Buffer (Depth Buffer) algorithm
7    Explain scan line algorithm
8.    Explain Depth Sort (Painter’s) Algorithm
9.    Explain BSP-Tree Method
10.    Explain Area-Subdivision Methods


UNIT – V

PART – A
1    What is the use of shading model?
            It is used to calculate the intensity of light that we should see at a given point on the surface of the object
2    What is diffuse illumination?
            The object may be illuminated by light which does not come from any particular source but which comes from all directions. When such illumination is uniform from all directions, the illumination is called diffuse illumination
3    What is diffuse reflection?
            When the reflection are constant over each surface of the object and they are independent of the viewing direction , the reflection is called diffuse reflection.
4    What is meant by Gouraud
shading?
             The shading technique which renders the polygon surface by linearly interpolating vertex intensity across the surface is called Gouraud shading.
5    What is meant by Phong shading?
          The shading technique which uses the bilinear interpolation of vertex normal instead of using vertex intensities is called Phong shading
6    What is specular reflection?
          When we illuminate a shiny surface such as polished metal or an apple with a bright light, we observe highlight or bright spot on the shiny surface. This phenomenon of reflection of incident light in a concentrated region around the specular reflection angle is called specular reflection.
7    What is faceted shading or flat shading?
          The fast and simple method for shading polygon is constant shading also known as faceted shading or flat shading
8    What is half toning?
          The phenomenon of apparent increase in the number of available intensities by considering combine intensity of multiple pixels is known as halftoning
9    What is refraction?
           Refraction is the bending of wave when it enters a medium where it’s speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media.
10    What is coefficient of reflection or the reflectivity?
             The ratio of the light reflected from the surface to the total incoming light to the surface is called coefficient of reflection or the reflectivity.
11    What is OpenGL?
            OpenGL is defined as a software interface to graphics hardware. It is a 3D graphics and modeling library that is extremely portable and very fast. OpenGL is a cross-platform standard for 3D rendering and D hardware acceleration. It is the premier environment for developing portable, interactive 2D and 3D graphics applications
12    Why OpenGL?
   It provides
    Device Independent
    Platform Independent; SGI Irix,Linux,Windows
    Abstractions(GL,GLU,GLUT)
    Open surface
    Hardware-independent software interface
    Support of client-server protocol
13    List some features of OpenGL
    Performance
    Lighting
    Transparency and Alpha blending
    Rendering in 3D
    Abstract co-ordinate system
    Color specification
    Drawing primitives
    Textures
Use of Hardware
14    List the libraries used in the OpenGL
     The libraries used in OpenGL are
    GL
    GLU
    GLUT
15    What is GL?
          The Gl is fundamental OpenGL library. It provides functions that are a permanent part of OpenGL
16    What is GLU?
           GLU is GL utility which helps in the decomposition of non convex and simple polygons into simple shapes such as triangles, and other utilities to simplify the job of the application programmer.
17    What is GLUT?
           The GL Utility Toolkit (GLUT) is an additional library that provides a generic interface to the window system and is available on most platform. An event driven model is used for handling input. Callback functions that respond to input events are registered with GLUT event loop.
18    What is Mach band?
                  The linear intensity interpolation can result bright or dark intensity streaks to appear on the surface. These bright or dark intensity streaks, are called Mach bands.
19    What is ambient light?
                 A simple way to model the combination of light reflection from the various suface to produce a uniform illumination called ambient light or background light
20    Advantages of Phong shading
    It displays more realistic highlights on a surface
    It greatly reduces the Mach-band effect
    It gives more accurate results
21   
What is meant by Rendering?
In 3D graphics rendering means the calculation of the final image from the scene that includes models, textures, lights, special effects and cameras. The final image will be 2D image made of pixels. Utilizing materials, lighting techniques, and renderer’s settings one can render multitude of different images from a single 3D scene.
22    Types of Rendering?
    Realistic rendering
    Clay Rendering
    Wire Rendering
23    List the advantages of flat shading?
    inexpensive to compute
    Appropriate for objects with flat surface
    Less pleasant for smooth surfaces


PART – B

1    Explain the following models
    Ambient Light
    Diffuse Illumination
    Pont-source Illumination
2    Explain the following models
    Specular Reflection
    Phong Illumination Model
3    Explain Gouraud Shading?
4    Explain Phong Shading?
5    Explain Halftone Shading
6    Explain Transparency
7    Explain Basic functions of OpenGL
8.    Explain features in OpenGL
9.    Explain how OpenGL works
10.    Explain OpenGL drawing primitives

CRYPTOGRAPHY AND NETWORK SECURITY QUESTION BANK

UNIT – I Introduction
PART-A

1.        What are the key principles of security?
Key properties of security:
To protect the data during transmission across the networks
• Authentication
• Confidentiality
• Integrity
• Access control

2.        Why network need security?
When systems are connected through the network, attacks are possible during transmission time.

3.        Define Encryption
The process of converting from plaintext to cipher text. Encryption is the science of changing data so that it is unrecognisable and useless to an unauthorised person.




4.        Specify the components of encryption algorithm.
1. Plaintext
2. Encryption algorithm
3. secret key
4. cipher text
5. Decryption algorithm

5.        Define confidentiality and authentication
Confidentiality:
It means how to maintain the secrecy of message. It ensures that the information in a computer system and transmitted information are accessible only for reading by authorized person.
Authentication:
It helps to prove that the source entity only has involved the transaction.

6.        Define cryptography.
It is a science of writing Secret code using mathematical techniques. The many schemes used for enciphering constitute the area of study known as cryptography.

7.        Specify the basic task for defining a security service.
A service that enhances the security of the data processing systems and the information transfer of an organization. The services are intended to counter security attack, and they make use of one or more security mechanism to provide the service.

8.        Explain active and passive attack with example?       
Passive attack:
Monitoring the message during transmission.                         
         Eg: Interception
      Active attack:                 
It involves the modification of data stream or creation of false data stream.          
                     E.g.: Fabrication, Modification, and Interruption

9.        Define integrity and nonrepudiation?         
     Integrity:
                   Service that ensures that only authorized person able to modify the message.
Nonrepudiation:                 
This service helps to prove that the person who denies the transaction is true or                
This service helps to prove that the person who denies the transaction is true or false. 

10.        Differentiate symmetric and asymmetric encryption?
 Symmetric
It is a form of cryptosystem in which encryption and decryption performed using the same key. 
Eg: DES, AES
Asymmetric
It is a form of cryptosystem in which encryption and decryption Performed using two keys.
Eg: RSA, ECC

11.        Define cryptanalysis?
             It is a process of attempting to discover the key or plaintext or both. 

12.        Define security mechanism 
It is process that is designed to detect prevent, recover from a security attack.
Example: Encryption algorithm, Digital signature, Authentication protocols. 


13.        Differentiate unconditionally secured and computationally secured
 An Encryption algorithm is unconditionally secured means, the condition is if the
cipher text generated by the encryption scheme doesn’t contain enough information to determine corresponding plaintext.
 Encryption is computationally secured means,
     1. The cost of breaking the cipher exceed the value of enough information.
     2. Time required to break the cipher exceed the  useful lifetime of information. 

14.        Define steganography
     Hiding the message into some cover media.  It conceals the existence of a message. 

15.        What are the essential ingredients of a symmetric cipher?
A symmetric cipher encryption has five ingredients. They are:
• Plaintext
• Encryption algorithm
• Secret key
• Cipher text
• Decryption algorithm

16.        What are the two basic functions used in encryption algorithms?
 The two basic functions used in encryption algorithms are
• Substitution
• Transposition
.
17.        Compare Substitution and Transposition techniques.
SUBSTITUTION
*A substitution techniques is one in which the letters of plaintext are replaced by other letter or by number or symbols.
*Eg: Caeser cipher.
TRANSPOSITION
* It means,different kind of mapping is achieved by performing some sort of permutation on the plaintext letters.
*Eg: DES, AES.

18.        Define Diffusion & confusion
Diffusion:
It means each plaintext digits affect the values of many ciphertext digits which is equivalent to each ciphertext digit is affected by many plaintext digits. It can be achieved by performing permutation on the data. It is the relationship between the plaintext  and ciphertext.
Confusion:
 It can be achieved by substitution algorithm. It is the relationship between ciphertext  and key.

19.        How many keys are required for two people to communicate via a cipher?
 If both sender and receiver use the same key, the system is referred to as symmetric, single key, secret key, or conventional encryption. If the sender and receiver each use a different key, the system is referred to as asymmetric, two-key, or public-key encryption.

20.        Define Decryption
    Decryption is the reverse operation of encryption. The process of decoding data that has been encrypted into a secret format. Decryption requires a secret key or password.







21.        What are the essential ingredients of a symmetric cipher?

A symmetric cipher encryption has five ingredients. They are:
• Plaintext
• Encryption algorithm
• Secret key
• Cipher text
• Decryption algorithm


PART-B
1.        Describe categories of Security Services in detail
2.        Briefly explain the categories of Security mechanisms
3.        List the categories of active security attack and explain any one active security attack
4.        List the categories of passive security attack and explain any one passive security attack
5.        Distinguish between active and passive security attacks and name possible active and passive security attacks
6.        List and describe security goals
7.        Write short notes on symmetric encryption.
8.        Write short notes on asymmetric encryption.
9.        Tabulate and explain the relationship between Security services and Mechanisms
10.        Write short notes on Substitution & Transposition cipher


UNIT II Symmetric Ciphers
PART A

1.        Differentiate symmetric and asymmetric encryption?
Symmetric It is a form of cryptosystem in which encryption and decryption performed using the same key.
E.g.: DES, AES
Asymmetric It is a form of cryptosystem in which encryption and decryption performed using two keys.
Eg: RSA, ECC

2.        What is a transposition cipher?
Transposition cipher is a cipher, which is achieved by performing some sort of permutation on the plaintext letters.

3.        Compare Substitution and Transposition techniques
SUBSTITUTION *A substitution techniques is one in which the letters of plaintext are replaced by other letter or by number or symbols.
*Eg: Caeser cipher.
TRANSPOSITION * It means, different kind of mapping is
achieved by performing some sort of permutation on the plaintext letters.
*Eg: DES, AES.

4.        Define Diffusion & confusion.
Diffusion:It means each plaintext digits affect the values of many cipher text digits which is equivalent to each cipher text digit is affected by many plaintext digits. It can be achieved by performing permutation on the data. It is the relationship between the plaintext and cipher text.
Confusion:It can be achieved by substitution algorithm. It is the relationship between cipher text and key.

5.        Why is it not practical to use an arbitrary reversible substitution cipher?

An arbitrary reversible cipher for a large block size is not practical, however, from an
implementation and performance point of view. Here the mapping itself is the key.


6.        What is the difference between diffusion and confusion?
          In diffusion, the statistical structure of the plain text is dissipated into long-range statistics of the cipher text. This is achieved by permutation.
In confusion, the relationship between the statistics of the cipher text and the value of the encryption key is made complex. It is achieved by substitution.

7.        What are the two approaches to attacking a cipher?
The two approaches to attack a cipher are:
• Cryptanalysis
• Brute-force attack

8.        Define the Caesar cipher
The Caesar cipher involves replacing each letter of the alphabet with the letter standing three places further down the alphabet. For example:
Plain: meet me after the toga party
Cipher: PHHW PH DIWHU WKH WRJD SDUWB

9.        Define the monoalphabetic cipher?
    A monoalphabetic cipher maps from a plain alphabet to cipher alphabet. Here a single cipher alphabet is used per message.

10.        Define the playfair cipher.
     The best-known multiple-letter encryption cipher is the playfair, which treats diagrams in the plain text as single units and translates these units into cipher text diagrams. The Playfair algorithm is based on the use of a 5x5 matrix of letters constructed using a keyword. In the case of keyword monarchy, matrix is as follows:
 M O N A R
C H Y B D
E F G I/J K
L P Q S T
U V W X Z

11.        What are the two problems with one-time pad?

• It makes the problem of making large quantities of random keys.
• It also makes the problem of key distribution and protection.


12.        What are the design parameters of Feistel cipher network?

*Block size
*Key size
*Number of Rounds
*Sub key generation algorithm
*Round function
*Fast software Encryption/Decryption
*Ease of analysis

13.        Define Product cipher.
It means two or more basic cipher are combined and it produce the resultant cipher is called the product cipher.

14.        Explain Avalanche effect.

A desirable property of any encryption algorithm is that a small change in either the plaintext or the key produce a significant change in the ciphertext. In particular, a change in one bit of the plaintext or one bit of the key should produce a change in many bits of the ciphertext. If the change is small, this might provider a way to reduce the size of the plaintext or key space to be searched.

15.        Give the five modes of operation of Block cipher.

1. Electronic Codebook(ECB)
2. Ciph    er Block Chaining(CBC)
3. Cipher Feedback(CFB)
4. Output Feedback(OFB)
5. Counter(CTR)

16.        State advantages of counter mode.
*Hardware Efficiency
*Software Efficiency
*Preprocessing
*Random Access
* Provable Security
*Simplicity.

17.        Define Multiple Encryption.

It is a technique in which the encryption is used multiple times.
Eg: Double DES, Triple DES


18.        Specify the design criteria of block cipher.
Number of rounds
Design of the function F
Key scheduling

19.        Define Reversible mapping.

Each plain text is maps with the unique cipher text. This transformation is called reversible mapping.


20.        Specify the basic task for defining a security service.

A service that enhances the security of the data processing systems and the information transfer of an organization. The services are intended to counter security attack, and they make use of one or more security mechanism to provide the service.


21.        What is the difference between link and end to end encryption?

Link Encryption End to End Encryption
1. With link encryption, each vulnerable 1.With end to end encryption, the Communications link is equipped on encryption process is carried out at Both ends with an encryption device the two end systems
2. Message exposed in sending host 2.Message encrypted in sending and and in intermediate nodes intermediate nodes
3. Transparent to user 3.User applies encryption
4 .Host maintains encryption facility 4.Users must determine algorithm
5. One facility for all users 5.Users selects encryption scheme
6. Can be done in hardware 6.Software implementations
7. Provides host authentication 7.Provides user authentication
8. Requires one key per(host-intermediate) 8.Requires one key per user pair Pair and (intermediate-intermediate)pair

22.        Why is the middle portion of 3DES a decryption rather than an encryption?

     Decryption requires that the keys be applied in reverse order: P=Dk1[Ek1[P]] This results in a dramatic increase in cryptographic strength.The use of DES results in a mapping that is not equivalent to a single DES encryption.


23.        What is the difference between the AES decryption algorithm and the equivalent inverse cipher?

     In AES decryption, we use inverse shift rows inverse sub bytes, add round key, inverse mix columns. But in equivalent inverse cipher, we interchange inverse shift rows and inverse sub bytes.

24.        What is traffic Padding? What is its purpose?

Traffic padding produces ciphertext output continuously, even in the absence of the plain text. A continuous random data stream is generated. When plain text is available, it is encrypted and transmitted. When input plaintext is not present, random data are encrypted and transmitted. This makes it impossible to for an attacker to distinguish between true dataflow and padding and therefore impossible to deduce the amount of traffic.


25.        What was the original set of criteria used by NIST to evaluate candidate AES cipher?

     The original set of criteria used by NIST to evaluate candidate AES cipher was:
• Security
• Actual Security
• Randomness
• Soundness
• Other security factors
• Cost
• Licensing Requirements
• Computational Efficiency
• Memory Requirements
• Algorithm And Implementation Characteristics
• Flexibility
• Hardware and software suitability
• Simplicity


26.        What was the final set of criteria used by NIST to evaluate candidate AES ciphers?

The final set of criteria used by NIST to evaluate candidate AES ciphers was:
• General Security
• Software Implementations
• Restricted-Space Environments
• Hardware Implementations
• Attacks On Implementations
• Encryption vs. Decryption
• Key Agility
Other Versatility And Flexibility
• Potential for Instruction-Level Parallelism

27.        What is power analysis?

    Power analysis is the power consumed by the smart card at any particular time during the
cryptographic operation is related to the instruction being executed and to the data being processed.


28.        What is the purpose of the State array?

A single 128-bit block is depicted as a square matrix of bytes. This block is copied into the State array, which is modified at each stage of encryption or decryption. After the final stage, State is copied to an output matrix.


29.        How is the S-box constructed?

    The S-box is constructed in the following fashion:
Initialize the S-box with the byte values in ascending sequence row by row. The first row contains {00}, {01}, {02}, ……….., {0F}; the second row contains {10},{11},etc; and so on. Thus, the value of the byte at row x, column y is {x y}. Map each byte in the S-box to its multiplicative inverse in the finite field GF (28); the value {00} is mapped to itself. Consider that each byte in the S-box consists of 8 bits labeled (b7,b6,b5,b4,b3,b2,b1,b0).Apply the following transformation to each bit of each byte in the S-box.

30.        Define Sub Bytes.

Sub byte uses an S-box to perform a byte-by-byte substitution of the block. The left most
4 bits of the byte are used as row value and the rightmost 4 bits are used as a column
value. These row and column values serve as indexes into the S-box to select a unique 8-
bit value.


31.        Define Shift Rows.
     In shift row, a row shift moves an individual byte from one column to another, which is a linear distance of a multiple of 4 bytes. In Forward Shift Row, each row perform circular left shift. Second Row a 1-byte circular left shift is performed. Third Row a 2-byte circular left shift is performed. For the Fourth Row a 3-byte circular left shift is performed. In Inverse Shift Row, each row perform circular right shift.

32.        How many bytes in State are affected by Shift Rows?

Totally 6-bytes in state are affected by Shift Rows.

33.        Define Mix Columns.

     Mix Column is substitution that makes use of arithmetic over GF(28).Mix Column operates on each column individually. Each byte of a column is mapped into a new value that is a function of all four bytes in the column. The Mix Column Transformation combined with the shift row transformation ensures that after a few rounds, all output bits depend on all input bits.


34.        Define Add Round Key.

     In Add Round Key, the 128 bits of State are bit wise XORed with the 128 bits of the round key. The operation is viewed as a column wise operation between the 4 bytes of a State column and one word of the round key; it can also be viewed as a byte-level operation. The Add Round Key transformation is as simple as possible and affects every bit of State.

35.        Define Key Expansion Algorithm.

     The AES key expansion algorithm takes as input a 4-word(16-byte) key and produces a linear array of 44 words(156 bytes). This is sufficient to provide a 4-word round key for
the initial Add Round Key stage and each of the 10 rounds of the cipher.
.

36.        What is the difference between Sub Bytes and Sub Word?

Sub Bytes: Sub Bytes uses an S-box to perform a byte-by-byte substitution of the block.
Sub Word: Sub Word performs a byte substitution on each byte of its input word,using the Sbox.
   

37.        What is the difference between Shift Rows and Rot Word?

Shift Rows: Shift Row is simple permutation. It shifts the rows circularly left or right.
Rot Word:Rot word performs a one-byte circular left shift on a word. This means that an
input word [b0,b1,b2,b3] is transformed into [b1,b2,b3,b0].


38.        Why do some block cipher modes of operation only use encryption while others use both encryption and decryption?

     Some block cipher modes of operation only use encryption because the input is set to some initialization vector and the leftmost bits of the output of the encryption function are XORed with the first segment of plain text p1 to produce the first unit of cipher text C1 and it is transmitted. While in decryption, the cipher text is XORed with the output of the encryption function to produce the plain text.

39.        What is triple encryption?

Tuchman proposed a triple encryption method that uses only two keys [TUCH79].
The function follows an encrypt – decrypt – encrypt (EDE) sequence. C=Ek1[Dk2[Ek1[P]]] There is no cryptographic significance to the use of decryption for the second stage. Its only advantage is that it allows users of 3DES to decrypt data encrypted by users of the older single DES: C=Ek1[Dk2[Ek1[P]]] = Ek1[P]


40.        What is a meet-in-the-middle attack?

     Meet-in-the-middle attack, was first described in [DIFF77]. It is based on the observation that, if we have C=Ek2[Ek1[P]] Then X=Ek1[P]=Dk2[C] Given a known pair, (P,C), the attack proceeds as follows. First, encrypt P for all 256 possible values of K1. Store these results in a table and then sort the table by the values of X. Next, decrypt C using all 256 possible values of K2. As each decryption is produced, check the result against the table for a match. If a match occurs, then test the two resulting keys against a new known plaintext-ciphertext pair. If the two keys produce the correct ciphertext, accept them as the correct keys.


41.        How many keys are used in triple encryption?

Tuchman proposed a triple encryption method that uses only two keys


PART-B

1.         Explain (a) Playfair cipher (b) Vernam cipher in detail.
2.        2. Convert “MEET ME” using Hill cipher with the key matrix Convert the cipher
text back to plaintext.
3.        Explain simplified DES with example.
4.        Write short notes on i) Steganography
5.        Explain classical Encryption techniques in detail.
6.        Write short notes on
(a) Security services
(b) Feistel cipher structure
7.        Explain Data Encryption Standard (DES) in detail.
8.        Briefly explain about DES design criteria?
9.        Briefly describe about the Strength of DES?
10.        Briefly explain Block Cipher modes of Operation
11.        Briefly explain about AES design criteria?
12.        Explain Triple DES with neat diagram
13.        How AES is used for encryption/decryption? Discuss with example.
14.        .List the evaluation criteria defined by NIST for AES


UNIT III ASYMMETRIC CIPHERS

1.        Differentiate public key and conventional encryption?           

Conventional Encryption    Public key Encryption

1. Same algorithm with the same used for encryption and decryption                      
    One algorithm is used for encryption Key is and decryption with a pair of keys
   
2. The sender and receiver must share                 and the key                                                                       2.The sender and receiver The algorithm must each have one of the Matched pair of keys    

3. The key must be secret               3.One of two keys must be kept  Secret                                                                                     

4. It must be impossible or atleast impractical decipher a message if no other information is available                                                                 4. It must be impossible or to at least impractical to decipher a message if no other  information is available                                                                                             

5.Knowledge of the algorithm plus samples must insufficient to determine the key.                                5. Knowledge of the algorithm of cipher text plus one of key plus samples of ciphertext must be insufficient to determine the other key. 

2.        What are the principle elements of a public key cryptosystem?
The principle elements of a cryptosystem are:                 
1.plain text                 
2.Encryption algorithm                 
3.Public and private key                
 4.Cipher text                 
                      5.Decryption algorithm 
3.        What are roles of public and private key?
               The two keys used for public-key encryption are referred to as the public key and the private key. Invariably, the private key is kept secret and the public key is known publicly. Usually the public key is used for encryption purpose and the private key is used in the decryption side.       
4.         Specify the applications of the public key cryptosystem?
The applications of the public-key cryptosystem can classified as follows
1. Encryption/Decryption: The sender encrypts a message with the recipient’s public key.
2. Digital signature: The sender “signs” a message with its private key. Signing is achieved by a cryptographic algorithm applied to a message or to a small block of data that is a function of the message.    
 3. Key Exchange: Two sides cooperate to exchange a session key. Several different    approaches are possible, involving the private key(s) of one or both parties. 
5.        What is the primitive root of a number?
We can define a primitive root of a number p as one whose powers generate all the integers from 1 to p-1. That is p, if a is a primitive root of the prime number p then the numbers. 
6.        . What is a one way function?
          
 One way function is one that map the domain into a range such that every function value has a unique inverse with a condition that the calculation of the function is easy where as the calculations of the inverse is infeasible.                                  
7.        What is a trapdoor one way function?     
It  is function which is easy to calculate in one direction and infeasible to calculate in other direction in the other direction unless certain additional information is known. With the additional information the inverse can be calculated in polynomial time.
8.        Describe in general terms an efficient procedure for picking a prime number?
The procedure for picking a prime number is as follows:
1. Pick an odd integer n at random (eg., using a pseudorandom number generator).
 2.   Pick an integer a<n at random.
3.   Perform the probabilistic primality test, such as Miller-Rabin.
If n fails the test, reject the value  n and go to step 1. 4.   If n has passed a sufficient number of tests, accept n; otherwise , go to step 2. 
9.        Determine the gcd(24140,16762) using Euclid’s algorithm.
We know, gcd(a,b)=gcd(b,a mod b)
gcd(24140,16762)=gcd(16762,7378)
gcd(7378,2006)=gcd(2006,1360)
gcd(1360,646)=gcd(646,68)
gcd(68,34)=34
gcd(24140,16762) = 34.

10.        Find gcd (1970, 1066) using Euclid’s algorithm?
gcd (1970,1066)   = gcd(1066,1970 mod 1066)                                      = gcd(1066,904)      = 2
                                             = 2
11.        Perform encryption and decryption using RSA alg. For the following. P=7; q=11; e=17; M=8.
     n=pq
n=7*11=77
ö(n)=(p-1) (q-1) =6*10 = 60
e=17
d =27
C= Me mod n
C = 817 mod 77 = 57
M = Cd mod n = 5727 mod 77 = 8

12.        What common mathematical constants are used in RC5?
     W :Word size in bits. RC5 encrypts 2-word blocks. 16,32,64
r: Number of rounds. 0,1,….,255 B Number of 8-bit bytes (octets) in the secret
key K. 0,1,….,255

13.        What are the steps in key generation algorithm in RSA algorithm.
1.    Generate two large random primes, p and q, of approximately equal size such that their product n = pq is of the required bit length, e.g. 1024 bits.
2.    Compute n = pq and (φ) phi = (p-1)(q-1).
3.    Choose an integer e, 1 < e < phi, such that gcd(e, phi) = 1.
4.    Compute the secret exponent d, 1 < d < phi, such that ed ≡ 1 (mod phi). The public key is (n, e) and the private key is (n, d).
5.    Keep all the values d, p, q and phi secret.
•    n is known as the modulus.
•    e is known as the public exponent or encryption exponent or just the exponent.
•    d is known as the secret exponent or decryption exponent.
14.        What are the steps involved in encryption process in RSA algorithm.
Obtains the recipient B's public key (n, e).
Represents the plaintext message as a positive integer m
Computes the ciphertext c = me mod n. Sends the ciphertext c to B.

15.        What are the steps involved in decryption process in RSA algorithm
Uses his private key (n, d) to compute m = cd mod n.
Extracts the plaintext from the message representative m.

16.        What are the steps involved in digital signing in RSA algorithm.
1.    Creates a message digest of the information to be sent.
2.    Represents this digest as an integer m between 0 and n-1.
3.    Uses her private key (n, d) to compute the signature s = md mod n.
4.    Sends this signature s to the recipient, B.
17.        What are the steps involved in Signature verification in RSA algorithm.
1.    Uses sender A's public key (n, e) to compute integer v = se mod n.
2.    Extracts the message digest from this integer.
3.    Independently computes the message digest of the information that has been signed.
4.    If both message digests are identical, the signature is valid.
18.        Perform encryption and decryption using RSA alg. For the following. P=7; q=11; e=17; M=8.
     n=pq
n=7*11=77
ö(n)=(p-1) (q-1) =6*10 = 60
e=17
d =27
C= Me mod n
C = 817 mod 77 = 57
M = Cd mod n = 5727 mod 77 = 8

19.        Define RC5.
RC5 is a block cipher notable for its simplicity. RC 5 is fast, symmetric block cipher suitable for hardware or software implementations.

20.        What common mathematical constants are used in RC5?
     W :Word size in bits. RC5 encrypts 2-word blocks. 16,32,64
r: Number of rounds. 0,1,….,255 B Number of 8-bit bytes (octets) in the secret
key K. 0,1,….,255

21.        What primitive operations are used in RC5?
     RC5 uses three primitive operations (and their inverse):
     • Addition: Addition of words, denoted by +, is performed modulo 2w. The inverse
operation, denoted by -, is subtraction modulo 2w.
• Bitwise exclusive-OR: This operation is denoted by “Å”.
• Left cicular rotation: The cyclic rotation of word x left by y bits is denoted by  x<<<y. The inverse is the right circular rotation of word x by y bits, denoted by x>>>y.


PART-B
1.        Define Fermat theorem and explain its application.
2.        Define Euler’s theorem and explain its application.
3.        Define Chinese remainder theorem and explain its application.
4.        Explain RSA algorithm in detail with an example.
5.        Briefly explain the idea behind Elliptic Curve Cryptosystem.
6.        Briefly explain Rabin cryptosystem.
7.        Explain Elgamal cryptosystem.
8.        Explain RC5 in detail.
9.        Compare Elliptic Curve Cryptosystem, Rabin cryptosystem and Elgamal cryptosystem.
10.        Explain primality testing algorithm?



UNIT IV MESSAGE INTEGRITY AND MESSAGE AUTHENTICATION

1.        What is message authentication?
         It is a procedure that verifies whether the received message comes from assigned source has not been altered. It uses message authentication codes, hash algorithms to authenticate the message. 

2.        Define the classes of message authentication function.
Message encryption: The entire cipher text would be used for authentication.
Message Authentication Code: It is a function of message and secret key produce a fixed length value.
Hash function: Some function that map a message of any length to fixed length which serves as authentication. 

3.        Specify the requirements for message authentication.
• Disclosure.
• Traffic analysis.
• Masquerade.
• Content Modification.
• Sequence Modification.
• Timing modification.
• Repudiation.

4.        What you meant by hash function?
           Hash function accept a variable size message M as input and produces a fixed size hash code H(M) called as message digest as output. It is the variation on the message authentication code. 

5.        Differentiate MAC and Hash function?
      MAC: In Message Authentication Code, the secret key shared by sender                                     and receiver. The MAC is appended to the message at the source at a time which the message is assumed or known to be correct.   
   Hash Function: The hash value is appended to the message at the source at time when the message is assumed or known to be correct. The hash function itself not considered to be secret. 

6.        Any three hash algorithm.
MD5 (Message Digest version 5) algorithm.
SHA_1 (Secure Hash Algorithm).
RIPEMD_160 algorithm.
7.        What are the requirements of the hash function?
H can be applied to a block of data of any size.    
H produces a fixed length output.
H(x) is relatively easy to compute for any given x, making both hardware and software implementations practical.

8.        What you meant by MAC?
         MAC is Message Authentication Code. It is a function of message and secret key which produce a fixed length value called as MAC.     MAC = Ck(M)
Where   M = variable length message          
  K = secret key shared by sender and receiver.         
CK(M) = fixed length authenticator.

9.        Differentiate internal and external error control.
      Internal error control:  In internal error control, an error detecting code also known as frame check sequence or checksum.      
External error control:  In external error control, error detecting codes are appended after encryption.

10.        What is the meet in the middle attack?
  This is the cryptanalytic attack that attempts to find the value in each of the range and domain of the composition of two functions such that the forward mapping of one through the first function is the same as the inverse image of the other through the second function-quite literally meeting in the middle of the composed function. 

11.        What is the role of compression function in hash function?
  The hash algorithm involves repeated use of a compression function f, that takes two inputs and produce a n-bit output. At the start of hashing the chaining variable has an initial value that is specified as part of the algorithm. The final value of the chaining variable is the hash value usually b>n; hence the term compression.

12.        Distinguish between direct and arbitrated digital signature?
Direct digital signature 
The direct digital signature involves only the communicating parties. This may be formed by encrypting the entire message with the sender’s private key.
Arbitrated Digital Signature
The arbiter plays a sensitive and crucial role in this digital signature. Every signed message from a sender x to a receiver y goes first to an arbiter A, who subjects the message and its signature to a number of tests to check its origin and content. 

13.        What are the properties a digital signature should have?
It must verify the author and the data and time of signature.
It must authenticate the contents at the time of signature.
It must be verifiable by third parties to resolve disputes. 

14.        What requirements should a digital signature scheme should satisfy?
The signature must be bit pattern that depends on the message being signed.
The signature must use some information unique to the sender, to prevent both forgery and denial.
It must be relatively easy to produce the digital signature.
    It must be relatively easy to recognize and verify the digital signature. 
It must be computationally infeasible to forge a digital signature, either by constructing a new message for an existing digital signature or by constructing a fraudulent digital signature for a given message.    
It must be practical to retain a copy of the digital signature in storage.

15.         Define Kerberos.         
Kerberos is an authentication service developed as part of project Athena at MIT. The problem that Kerberos address is, assume an open distributed environment in which users at work stations wish to access services on servers distributed throughout the network. 

16.        What is Kerberos? What are the uses?
 Kerberos is an authentication service developed as a part of project Athena at MIT. Kerberos provide a centralized authentication server whose functions is to authenticate servers. 

17.        What 4 requirements were defined by Kerberos?
Secure
Reliable
Transparent
Scalable

18.        In the content of Kerberos, what is realm?        
A full service Kerberos environment consisting of a Kerberos server, a no. of clients, no. of application server requires the following:
The Kerberos server must have user ID and hashed password of all participating users in its database.
The Kerberos server must share a secret key with each server. Such an
environment is referred to as “Realm”. 

19.        What is the purpose of X.509 standard?         
 X.509 defines framework for authentication services by the X.500 directory to its users.X.509 defines authentication protocols based on public key certificates

20.        What are the services provided by PGP services
Digital signature
Message encryption
Compression
           E-mail compatibility
      Segmentation     

21.        Why E-mail compatibility function in PGP needed?
                 Electronic mail systems only permit the use of blocks consisting of ASCII text. To accommodate this restriction PGP provides the service converting the row 8-bit binary stream to a stream of printable ASCII characters. The scheme used for this purpose is Radix-64 conversion.        

22.        Name any cryptographic keys used in PGP?
                    a) One-time session conventional keys.                    
        b) Public keys.                    
        c) Private keys.                    
        d) Pass phrase based conventional keys.          

23.        Define key Identifier?
                    PGP assigns a key ID to each public key that is very high probability unique with a user ID. It is also required for the PGP digital signature. The key ID               associated with each public key consists of its least significant 64bits.       

24.        Specify the techniques for distribution of public key.
• Public announcement.
• Publicly available directory.
• Public key authority.
• Public key certificate
25.        Assume the client C wants to communicate server S using Kerberos procedure.
How can it be achieved?
a) C || AS: [IDC|| PC || IDV]
b) AS || C: Ticket
c) C || V: [IDC || ADC || IDV]
Ticket = EKV [IDC ||ADC || IDV]

26.        Specify the four categories of security threats
• Interruption
• Interception
• Modification
• Fabrication

27.        Define PGP
Pretty Good Privacy (PGP) is a popular program used to encrypt and decrypt e-mail over the Internet. It can also be used to send an encrypted digital signature that lets the receiver verify the sender's identity and know that the message was not changed en route

28.        Define Certification Authority
Certificate authority or Certification authority (CA) is an entity that issues digital certificates. The digital certificate certifies the ownership of a public key by the named subject of the certificate. This allows others (relying parties) to rely upon signatures or assertions made by the private key that corresponds to the public key that is certified. In this model of trust relationships, a CA is a trusted third party that is trusted by both the subject (owner) of the certificate and the party relying upon the certificate. CAs are characteristic of many public key infrastructure (PKI) schemes.


PART-B

1.    Explain Authentication Functions.
2.    Briefly Explain HMAC algorithm.
3.    Describe RIPEMD-160.
4.    Explain Hash Functions.
5.    Explain Digital Signature Standard.
6.    Briefly explain about MD5 algorithm?
7.    Briefly describe about the Secure Hash Algorithm?
8.    Explain authentication protocol
9.    Explain the classification of authentication function in detail
10.     Describe MD5 algorithm in detail. Compare its performance with SHA-1.
11.    Describe SHA-1 algorithm in detail. Compare its performance with MD5 and
RIPEMD-160 and discuss its advantages.
12.    Describe RIPEMD-160 algorithm in detail. Compare its performance with MD5 and SHA-1.
13.     Describe HMAC algorithm in detail.
14.    Write and explain the Digital Signature Algorithm.
15.    Assume a client C wants to communicate with a server S using Kerberos protocol. How can it be achieved?
16.    Define Kerberos Version 4.
17.    Define Kerberos Version 5.
18.    Explain briefly about X.509 Authentication Service.
19.    Discuss about the concept of Electronic Mail Security.
20.    Define S/MIME.
21.    Discuss briefly about IP Security.
22.    Explain with elaborate about the Web Security Considerations.
23.    Explain briefly about the Secure Electronic Transaction.
24.     Explain in detail about the IP Security Architecture
25.     Explain in detail about the Authentication Header.
     26.    Discuss briefly about Pretty Good Privacy.

UNIT V ADVANCED NETWORK SECURITY
22.        Define WAP
    Wireless application protocol (WAP) is an application environment and a set of communication protocols for wireless devices designed to give manufacturer, vendor, and technology-independent access to the Internet and advanced telephony services.
23.        Define WTLS
    Wireless transport layer security (WTLS), an optional security layer, has encryption facilities that provide the secure transport service required by many applications, such as e-commerce.
    WTLS is designed to support the security requirements of authentication, privacy, and integrity in the Wireless Application Protocol (WAP) defined by the WAP Forum. 
24.        Define GSM
    Global System for Mobile Communications is voice technology widely used in Europe.
25.        Define GPRS
    General Packet Radio Service is an emerging wireless data service that offers a mobile data experience similar to current analog modems without wires and with access wherever GSM wireless is available

26.        What are the key aspects to GSM Security?
    Three key aspects to GSM Security
        Subscriber identity authentication
        Signaling data confidentiality
        User data confidentiality
27.        What are the services needed in GSM Security?
Authentication
Signaling and data confidentiality
Voice and data security
28.        What are technologies used in java cryptography?
    The technologies used in java cryptography are
        Java Cryptography Architecture (JCA)
        Java Cryptography Extension (JCE)
29.        What are TCP/IP VULNERABILITIES?
        Spoofing
        Session hijacking
        Sequence guessing
        Lack of authentication and encryption
        SYN flooding
30.        What are security services in UNIX?
    Access Control
    User Authentication
31.        What are the security features in Windows 2000?
    Secure login with anti spoofing measures
    Discretionary access controls
    Privileged access controls
    Address space protection
    New page zeroing
    Security auditing
32.        Define firewall
    A firewall is a set of related programs, located at a network gateway server that protects the resources of a private network from users from other networks.
33.        What are the types of firewall?
        Packet filters
        Application Gateway
34.        Define Packet filters
    A Packet filter applies a set of rules to each packet and based on outcome, decides to either forward or discard the packet. Also called as Screening router or screening filter.
35.        What are the techniques used in security of Packet filter?
    IP address Spoofing
    Source routing attacks
    Tiny fragment attacks
36.        Define Application Gateways
    An Application gateways acts like a proxy and decides about the flow of application level traffic. Also called as a proxy server.
37.        What are the Firewall configurations?
    Screened host firewall, Single-homed bastion
    Screened host firewall, Dual-homed bastion
    Screened subnet firewall
38.        What are the limitations of Firewall?
    Insider’s intrusion
    Direct Internet traffic
    Virus attacks
   
39.        Define VPN
    Virtual Private Networks is a mechanism of employing encryption, authentication and integrity protection so that we can use a public network as if it is a private network.
40.        What are the three main VPN protocols?
    Point to point tunneling protocol
    Layer 2 Tunneling protocol
    IPSec
41.        What is Single Sign On (SSO)?
    SSO provides a single authentication interface to end users. Based on two broad level approaches.
        Script approach
        Agent approach

PART-B
11.        Explain Wireless Application Protocol Security.
12.        Explain security in GSM in detail.
13.        Explain security in 3G in detail.
14.        Explain security in java in detail.
15.        Explain security in Operating System in detail.
16.        Define firewall and explain its types.
17.        Explain firewall configuration.
18.         Define Virtual private network and explain its protocols.
19.        Explain case studies on SSO.
20.        Explain case studies on DOS.
21.        Explain case studies on CSSV.