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# Cryptography And Network Security Principles and Practice 6th Edition by William Stallings Test Bank

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Cryptography And Network Security Principles and Practice 6th Edition by William Stallings Test Bank

Sample  Questions

Chapter 3:  Block Ciphers and the Data Encryption Standard

TRUE OR FALSE

T          F          1.  The vast majority of network based symmetric cryptographic

applications make use of stream ciphers.

T          F          2.  The Feistel cipher structure, based on Shannons proposal of 1945,

dates back over a quarter of a century and is the structure used by

many significant symmetric block ciphers currently in use.

T          F          3.  DES uses a 56-bit block and a 64-bit key.

T          F          4.  If the bit-stream generator is a key-controlled algorithm the two

users only need to share the generating key and then each can

produce the keystream.

T          F          5.  A problem with the ideal block cipher using a small block size is

that it is vulnerable to a statistical analysis of the plaintext.

T          F          6.  Confusion seeks to make the statistical relationship between the

plaintext and ciphertext as complex as possible in order to thwart

attempts to deduce the key.

T          F          7.  All other things being equal, smaller block sizes mean greater

security.

T          F          8.  Greater complexity in the subkey generation algorithm should lead

to greater difficulty of cryptanalysis.

T          F          9.  Fast software encryption/decryption and ease of analysis are two

considerations in the design of a Feistel cipher.

T          F          10. A prime concern with DES has been its vulnerability to brute-force

attack because of its relatively short key length.

T          F          11. One criteria for an S-box is:  If two inputs to an S-box differ in

exactly one bit, the outputs must also differ in exactly one bit.

T          F          12. The heart of a Feistel block cipher is the function F, which relies

on the use of S-boxes.

T          F          13. The strict avalanche criterion and the bit independence criterion

appear to weaken the effectiveness of the confusion function.

T          F          14. An advantage of key-dependent S-boxes is that because they are

not fixed, it is impossible to analyze the S-boxes ahead of time to

look for weaknesses.

T          F          15.  The key schedule algorithm is more popular and has received

more attention than S-box design.

MULTIPLE CHOICE

1. DES exhibits the classic __________ block cipher structure, which consists of a number of identical rounds of processing.

1. A) Feistel B) SAC

1. C) Shannon D) Rendell

1. A sequence of plaintext elements is replaced by a __________ of that sequence which means that no elements are added, deleted or replaced in the sequence, but rather the order in which the elements appear in the sequence is changed.

1. A) permutation B) diffusion

1. C) stream D) substitution

1. A __________ cipher is one that encrypts a digital data stream one bit or one byte at a time.

1. A) product B) block

1. C) key D) stream

1. The vast majority of network-based symmetric cryptographic applications make use of ________ ciphers.

1. A) linear B) block

1. C) permutation D) stream

1. A __________ cipher is one in which a block of plaintext is treated as a whole and used to produce a ciphertext block of equal length.

1. A) bit B) product

1. C) stream D) block
2. __________ is when each plaintext element or group of elements is uniquely replaced by a corresponding ciphertext element or group of elements.

1. A) Substitution B) Diffusion

1. C) Streaming D) Permutation

1. Key sizes of __________ or less are now considered to be inadequate.

1. A) 128 bits B) 32 bits

1. C) 16 bits D) 64 bits

1. Feistel proposed that we can approximate the ideal block cipher by utilizing the concept of a __________ cipher, which is the execution of two or more simple ciphers in sequence in such a way that the final result or product is cryptographically stronger than any of the component ciphers.

1. A) linear B) permutation

1. C) differential D) product

1. The criteria used in the design of the __________ focused on the design of the  S-boxes and on the P function that takes the output of the S-boxes.

1. A) Avalanche Attack B) Data Encryption Standard

1. C) Product Cipher D) Substitution Key

1. The greater the number of rounds, the __________ it is to perform cryptanalysis.
2. A) easier B) less difficult

1. C) equally difficult D) harder

1. The function F provides the element of __________ in a Feistel cipher.

1. A) clarification B) alignment

1. C) confusion D) stability

1. One of the most intense areas of research in the field of symmetric block ciphers is __________ design.

1. A) S-box B) F-box

1. C) E-box D) D-box

1. Mister and Adams proposed that all linear combinations of S-box columns should be _________ which are a special class of Boolean functions that are highly nonlinear according to certain mathematical criteria.

1. A) horizontal functions B) angular functions

1. C) bent functions D) vertical functions

1. The Nyberg approach that is more or less a manual approach with only simple mathematics to support it is __________ .

1. C) math-made D) random with testing

1. Allowing for the maximum number of possible encryption mappings from the plaintext block is referred to by Feistel as the __________ .

1. A) ideal substitution cipher B) round function

1. C) ideal block cipher D) diffusion cipher

1. A _________ is an encryption/decryption scheme in which a block of plaintext is treated as a whole and used to produce a ciphertext block of equal length.

1. __________ seeks to make the relationship between the statistics of the ciphertext and the value of the encryption key as complex as possible so that even if the attacker can get some handle on the statistics of the ciphertext, the way in which the key was used to produce that ciphertext is so complex it is difficult to deduce the key.

1. Many block ciphers have a __________ structure which consists of a number of identical rounds of processing and in each round a substitution is performed on one half of the data being processed, followed by a permutation that interchanges the two halves.

1. Feistels is a practical application of a proposal by Claude Shannon to develop a product cipher that alternates confusion and ________ functions.

1. The __________ criterion is defined as: An S-box satisfies GA of order y if, for a 1-bit input change, at least y output bits change.

1. In ___________ the statistical structure of the plaintext is dissipated into long-range statistics of the ciphertext. This is achieved by having each plaintext digit affect the value of many ciphertext digits.

1. The most widely used encryption scheme is based on the __________ adopted in 1977 by the National Bureau of Standards as Federal Information Processing Standard 46.

1. A change in one bit of the plaintext or one bit of the key should produce a change in many bits of the ciphertext. This is referred to as the __________ effect.

1. Two areas of concern regarding the level of security provided by DES are the nature of the algorithm and the __________ .

1. A _________ attack exploits the fact that an encryption or decryption algorithm often takes slightly different amounts of time on different inputs.

1. The __________ criterion states that output bits j and k should change independently when any single input bit i is inverted for all i, j and k.

1. The ________ cipher structure, which dates back over a quarter century and which, in turn, is based on Shannons proposal of 1945, is the structure used by many significant symmetric block ciphers currently in use.

1. The cryptographic strength of a Feistel cipher derives from three aspects of the design: the function F, the key schedule algorithm, and __________ .

1. The __________ criterion states that any output bit j of an S-box should change with probability 1/2 when any single input bit i is inverted for all i,j.

1. Two alternatives to DES are AES and _________ DES.

TRUE OR FALSE

T          F          1.  AES uses a Feistel structure.

T          F          2.  At each horizontal point, State is the same for both encryption and

decryption.

T          F          3.  DES is a block cipher intended to replace AES for commercial

applications.

T          F          4.  The nonlinearity of the S-box is due to the use of the multiplicative

inverse.

T          F          5.  Virtually all encryption algorithms, both conventional and public-

key, involve arithmetic operations on integers.

T          F          6.  Compared to public-key ciphers such as RSA, the structure of AES

and most symmetric ciphers is quite complex and cannot be

explained as easily as many other cryptographic algorithms.

T          F          7.  InvSubBytes is the inverse of ShiftRows.

T          F          8.  The ordering of bytes within a matrix is by column.

T          F          9.  In the Advanced Encryption Standard the decryption algorithm is

identical to the encryption algorithm.

T          F          10. The S-box is designed to be resistant to known cryptanalytic

attacks.

T          F          11. As with any block cipher, AES can  be used to construct a message

authentication code, and for this, only decryption is used.

T          F          12. The inverse add round key transformation is identical to the

forward add round key transformation because the XOR

operation is its own inverse.

T          F          13. The Rijndael developers designed the expansion key algorithm to

be resistant to known cryptanalytic attacks.

T          F          14. The transformations AddRoundKey and InvMixColumn alter the

sequence of bytes in State.

T          F          15. AES can be implemented very efficiently on an 8-bit processor.

MULTIPLE CHOICE

1. ARK B.  FIPS

1. IEEE D.  NIST

1. In Advanced Encryption Standard all operations are performed on __________

bytes.

1. 8-bit                                   B.  16-bit

1. 32-bit                                 D.  4-bit

1. The AES cipher begins and ends with a(n) _________ stage because any other stage,

applied at the beginning or end, is reversible without knowledge of the key and

1. MixColumns                                  D.  ShiftRows

1. A __________ is a set in which you can do addition, subtraction, multiplication and

division without leaving the set.

1. record                                           B.  standard

1. field                                                D.  block

1. Division requires that each nonzero element have a(n) __________ inverse.

1. multiplicative                    B.  divisional

1. In AES, the arithmetic operations of addition, multiplication and division are

performed over the finite field _________ .

1. Zp                                       B.  a/b = a(b-1)

1. GF(2n-1)                              D.  GF(28)

1. In the AES structure both encryption and decryption ciphers begin with a(n)

__________ stage, followed by nine rounds that each include all four stages,

followed by a tenth round of three stages.

1. MixColumns                                  D.  ShiftRows

1. The final round of both encryption and decryption of the AES structure consists

of __________ stages.

1.   one                                    B.  two

1.   four                        D.  three

1. The first row of State is not altered; for the second row a 1-byte circular left

shift is performed; for the third row a 2-byte circular left shift is performed; and

for the fourth row a 3-byte circular left shift is performed.  This transformation

is called __________ .

1. MixColumns                      D.  Substitute bytes

1. In the AddRoundKey transformation the 128 bits of State are bitwise XORed

with the _________ of the round key.

1. 256 bits B.  128 bits

1. 64 bits                               D.  512 bits

1. The __________ is when a small change in plaintext or key produces a large change

in the ciphertext.

1. avalanche effect                           B.  Rcon

1. key expansion                              D.  auxiliary exchange

1. The encryption round has the structure:

1. ShiftRows, MixColumns, SubBytes, InvMixColumns

1. __________ affects the contents of bytes in State but does not alter byte sequence

and does not depend on byte sequence to perform its transformation.

1. InvSubBytes                     B.  ShiftRows

1. SubBytes                           D.  InvShiftRows

1. In the general structure of the AES encryption process the input to the

encryption and decryption algorithms is a single _________ block.

1. 32-bit                                 B.  256-bit

1. 128-bit                               D.  64-bit

1. The cipher consists of N rounds, where the number of rounds depends on the

__________ .

1. key length                         B.  output matrix

1. State                                   D.  number of columns

1. The __________ is a block cipher intended to replace DES for commercial applications.  It uses a  128-bit block size and a key size of 128, 192, or 256 bits.

1. The four separate functions of the Advanced Encryption Standard are: permutation, arithmetic operations over a finite field, XOR with a key, and __________ .

1. The National Institute of Standards and Technology chose the __________ design as the winning candidate for AES.

1. The cipher consists of N rounds, where the number of rounds depends on the __________ .

1. AES processes the entire data block as a single matrix during each round using __________ and permutation.

1. The first N 1 rounds consist of four distinct transformation functions: SubBytes, ShiftRows, AddRoundKey, and __________ .

1. The forward substitute byte transformation, called _________ , is a simple table lookup.

1. The _________ transformation 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 that column.

1. The mix column transformation combined with the __________ transformation ensures that after a few rounds all output bits depend on all input bits.

1. The AES key expansion algorithm takes as input a four-word (16-byte) key and produces a linear array of __________ words (176 bytes).

1. The standard decryption round has the structure InvShiftRows, InvSubBytes, __________, InvMixColumns.

1. ___________ affects the sequence of bytes in State but does not alter byte contents and does not depend on byte contents to perform its transformation.

1. A more efficient implementation can be achieved for a 32-bit processor if operations are defined on _________ words.

1. An example of a finite field is the set Zp consisting of all the integers {0, 1, . . . ,  p 1}, where p is a __________ and in which arithmetic is carried out modulo p.

1. A polynomial m(x) is called __________ if and only if m(x) cannot be expressed as a product of two polynomials, both of degree lower than that of m(x).

Chapter 7:  RANDOM and Pseudorandom Number

Generation and Stream Ciphers

TRUE OR FALSE

T          F          1.  The principle requirement of random or pseudorandom number

generation is that the generated number stream be unpredictable.

T          F          2.  Random numbers play an important role in the use of encryption

for various network security applications.

T          F          3.  There are well-defined tests for determining uniform distribution

and independence to validate that a sequence of numbers is

random.

T          F          4.  With true random sequences each number is statistically

independent of other numbers in the sequence and therefore

unpredictable.

T          F          5.  The true random number generator may simply involve conversion

of an analog source to a binary output.

T          F          6.  Examples of a pseudorandom function are decryption keys and

nonces.

T          F          7.  If the PRF does not generate effectively random 128-bit output

values it may be possible for an adversary to narrow the

possibilities and successfully use a brute force attack.

T          F          8.  The purpose of the Maurers universal statistical test is to

determine whether the number of ones and zeros in a sequence

are approximately the same as would be expected for a truly

random sequence.

T          F          9.  The seed that serves as input to the PRNG must be secure for

cryptographic applications.

T          F          10. Three broad categories of cryptographic algorithms are commonly

used to create PRNGs:  symmetric block ciphers, asymmetric

ciphers, and hash functions and message authentication codes.

T          F          11. A widely used technique for pseudorandom number generation is

an algorithm known as the linear congruential method.

T          F          12. A cryptographically secure pseudorandom bit generator is defined

as one that passes the least significant bit test.

T          F          13. The security of Blum, Blum, Shub is based on the difficulty of

factoring n.

T          F          14. The stream cipher is similar to the one-time pad with a difference

being that a one-time pad uses a pseudorandom number stream

and a stream cipher uses a genuine random number stream.

T          F          15. The longer the keyword the more difficult the cryptanalysis.

MULTIPLE CHOICE

1. A secret key for symmetric encryption that is generated for use for a short period of time is called a _________ .

1. strategic key B.  sequence key

1. session key D.  stream key

1. A __________ is used to produce a pseudorandom string of bits of some fixed length.

1. PRF B.  PRNG

1. OFB PRNG D.  TRNG

1. A source that is effectively random is referred to as a(n) __________ .

1. open source B.  entropy source

1. keystream D.  seed

1. A __________ takes as input a source that is effectively random.

1. PRF B.  BBS

1. PRNG D.  TRNG
2. A pseudorandom number generator takes as input a fixed value called the

__________ and produces a sequence of output bits using a deterministic algorithm.

1. seed                                   B.  fixed skew

1. entropy source                 D.  keystream

1. The best that can be done to determine if a PRNG generates numbers that have the characteristic of randomness is on the basis of multiple tests. These tests should seek to establish uniformity, scalability, and __________ .

1. consistency B.  authentication

1. frequency D.  sequencing

1. The __________ test is the most basic test of randomness and must be included in any test suite.

1. frequency B.  runs

1. unpredictability D.  Maurer

1. The Blum, Blum, Shub generator is referred to as a ____________ .

1. TRNG B.  OFB PRNG

1. QRN D.  CSPRBG

1. Two approaches that use a block cipher to build a PNRG and have gained widespread acceptance are:

1. CTR mode and CFB mode B.  CTR mode and OFB mode

1. CBC mode and CFB mode D.  OFB mode and ECB mode

1. A __________ uses a nondeterministic source to produce randomness.

1. CSPRBG B.  TRNG

1. PRNG D.  BBS
2. __________ is an open source project for creating truly random numbers using inexpensive cameras, open source code, and inexpensive hardware.

1. LavaRnd                                        B.  Blum, Blum, Shub

1. Maurers statistics                        D.  Entropy

1. Various methods of modifying a bit stream to reduce or eliminate a bias have been developed. These are referred to as ___________ algorithms.

1. backward B.  deskewing

1. forward D.  keystream

1. The Linux operating system uses _________ entropy sources for generating random numbers.

1. four B.  three

1. one D.  two

1. In key distribution and reciprocal authentication schemes two communicating parties cooperate by exchanging messages to distribute keys and/or authenticate each other. In many cases ___________ are used for handshaking to prevent replay attacks.

1. session keys B.  nonces

1. RC4s D.  entropies

1. The distribution of bits in a random number sequence should be ___________ , therefore the frequency of occurrence of ones and zeros should be approximately equal.

1. independent B.  uniform

1. reversed D.  streamed

1. A __________ is a symmetric encryption algorithm in which ciphertext output is produced bit-by-bit or byte-by-byte from a stream of plaintext input.

1. Typically the __________ takes as input a seed plus some context specific values such as a user ID or an application ID.

1. Two criteria used to validate that a sequence of numbers is random are uniform distribution and __________ .

1. The most important and widely used stream cipher is __________ .

1. Two distinct requirements for a sequence of random numbers are unpredictability and __________ .

1. If the algorithm is good the resulting sequences will pass many reasonable tests of randomness. These numbers are referred to as ___________ numbers.

1. The __________ is drawn from the physical environment of the computer and could include things such as keystroke timing patterns, disk electrical activity, mouse movements, and instantaneous values of the system clock.

1. An algorithm that is used to produce an open-ended sequence of bits is referred to as a ___________ .

1. The purpose of the __________ test is to determine whether the number of runs of ones and zeros of various lengths is as expected for a random sequence.

1. A stream of pseudorandom numbers should exhibit two forms of unpredictability: forward and __________ .

1. __________ algorithms are designed specifically and solely for the purpose of generating pseudorandom bit streams.

1. In a stream cipher structure a key is input to a pseudorandom bit generator that produces a stream of 8-bit numbers that are apparently random. The output of the generator, called a ___________ , is combined one byte at a time with the plaintext stream using the bitwise exclusive-OR operation.

1. __________ is a stream cipher designed in 1987 by Ron Rivest for RSA Security.

1. Operating systems typically provide a built-in mechanism for generating random numbers. For example,  __________ uses mouse and keyboard activity, disk I/O operations, and specific interrupts.

1. A fundamental requirement of the RSA public-key encryption scheme is the ability to generate _________ numbers.

Chapter 9:  Public-Key Cryptography and RSA

TRUE OR FALSE

T          F          1.   Asymmetric encryption utilizes only a public key for encryption

and decryption.

T          F          2.  Asymmetric encryption can be used for confidentiality but not for

authentication.

T          F          3.  Asymmetric encryption transforms plaintext into ciphertext.

T          F          4.  Plaintext is transformed into ciphertext using two keys and a

decryption algorithm.

T          F          5.  A major advance in symmetric cryptography occurred with the

development of the rotor encryption/decryption machine.

T          F          6.  Public-key encryption is more secure from cryptanalysis than

symmetric encryption.

T          F          7.  Much of the theory of public-key cryptosystems is based on

number theory.

T          F          8.  Asymmetric algorithms rely on one key for encryption and a

different but related key for decryption.

T          F          9.  The encryption algorithm performs various transformation on the

ciphertext.

T          F`         10. If the authenticator is encrypted with the senders private key, it

serves as a signature that verifies origin, content, and sequencing.

T          F          11. A trap-door one-way function is easy to calculate in one direction

and infeasible to calculate in the other direction unless certain

T          F          12. A public-key encryption scheme is not vulnerable to a brute-force

attack.

T          F          13. Before the application of the public-key cryptosystem each

participant must generate a pair of keys.

T          F          14. The defense against the brute-force approach for RSA is to use a

large key space.

T          F          15. Timing attacks are ciphertext attacks that are only applicable to

RSA.

MULTIPLE CHOICE

1. Asymmetric encryption is also known as ___________ .

1. public-key encryption B.  private-key encryption

1. optimal encryption D.  digital-key encryption

1. Public-key encryption is also known as ___________ .

1. digital-key encryption B.  asymmetric encryption

1. one way time exchange encryption D.  optimal-key encryption

1. Asymmetric encryption can be used for __________ .

1. both confidentiality and authentication

1. neither confidentiality nor authentication

1. confidentiality

1. authentication

1. Plaintext is recovered from the ciphertext using the paired key and a _____________ .

1. digital signature B.  recovery encryption

1. decryption algorithm D.  encryption algorithm

1. The most widely used public-key cryptosystem is __________ .

1. optimal asymmetric encryption

1. asymmetric encryption

1. RSA

1. DES

1. Public-key algorithms are based on __________ .

1. permutation B.  mathematical functions

1. substitution D.  symmetry

1. __________ are two related keys, a public key and a private key that are used to perform complementary operations, such as encryption and decryption or signature generation and signature verification.

1. Asymmetric keys B.  Key exchanges

1. Symmetric keys D.  Cipher keys

1. The __________ indicates that the subscriber identified in the certificate has sole control and access to the private key.

1. OAEP B.  Public Key Certificate

1. Digital Signature D.  PKI

1. A __________ is a cryptographic algorithm that uses two related keys, a public key and a private key. The two keys have the property that deriving the private key from the public key is computationally infeasible.

1. Private Key (Symmetric) Cryptographic Algorithm

1. Key Exchange Cryptographic Algorithm

1. Public Key (Asymmetric) Cryptographic Algorithm

1. RSA Digital Cryptographic Algorithm

1. A public-key encryption scheme has __________ ingredients.

1. six B.  four

1. eight D.  two

1. The key used in symmetric encryption is referred to as a __________ key.

1. public B.  secret

1. private D.  decryption

1. The readable message or data that is fed into the algorithm as input is the ____________ .

1. ciphertext B.  exchange

1. plaintext D.  encryption

1. Two issues to consider with the computation required to use

RSA are encryption/decryption and __________ .

1. time complexity B.  trap-door one-way functions

1. key generation D.  asymmetric encryption padding

1. __________ depend on the running time of the decryption algorithm.

1. Mathematical attacks B.  Timing attacks

1. Chosen ciphertext attacks D.  Brute-force attacks

1. We define the ___________ of an algorithm to be f(n) if, for all n and all inputs of length n the execution of the algorithm takes at most f(n) steps.  This is a common measure of the efficiency of an algorithm.

1. time complexity B.  one-way function

1. timing attack D.  OAEP

1. __________ encryption is a form of cryptosystem in which encryption and decryption are performed using a public key and a private key.

1. A __________ is when two sides cooperate to exchange a session key.

1. Asymmetric encryption transforms plaintext into __________ using one of two keys and an encryption algorithm.

1. The difficulty of attacking __________ is based on the difficulty of finding the prime factors of a composite number.

1. Public-key cryptography is asymmetric, involving the use of two separate keys, in contrast to ___________ encryption, which uses only one key.

1. A __________ is a digital document issued and digitally signed by the private key of a Certification Authority that binds the name of a subscriber to a public key.

1. The __________ is a set of policies, processes, server platforms, software and workstations used for the purpose of administering certificates and public-private key pairs, including the ability to issue, maintain, and revoke public key certificates.

1. The scrambled message produced as output is the __________ . It depends on the plaintext and the key.

1. A __________ is one that maps a domain into a range such that every function value has a unique inverse, with the condition that the calculation of the function is easy, whereas the calculation of the inverse is infeasible.

1. The sender signs a message with its private key. Signing is

achieved by a cryptographic algorithm applied to the message

or to a small block of data that is a function of the message, is

a description of a ___________ .

1. The __________ scheme is a block cipher in which the plaintext

and ciphertext are integers between 0 and n 1 for some n.

1. A single algorithm that will calculate the greatest common

divisor (gcd) of two integers and, if the gcd is 1, determine the inverse of one of the integers modulo the other, is the __________ algorithm.

1. Four possible approaches to attacking the RSA algorithm are:

brute force, mathematical attacks, chosen ciphertext attacks, and ___________ .

1. A __________ is an attack in which the adversary chooses a

number of ciphertexts and is then given the corresponding plaintexts, decrypted with the targets private key.

1. To counter attacks such as CCAs, RSA Security, Inc.

recommends modifying the plaintext using a procedure known as ___________ .

Chapter 11:  Cryptographic Hash Functions

TRUE OR FALSE

T          F          1.  Virtually all cryptographic hash functions involve the iterative use

of a compression function.

T          F          2.  A good hash function has the property that the results of applying

the function to a large set of inputs will produce outputs that are

evenly distributed and apparently random.

T          F          3.  Limited characteristics make it impossible for hash functions to be

used to determine whether or not data has changed.

T          F          4.  Hash functions can be used for intrusion and virus detections.

T          F          5.  Whirlpool is a popular cryptographic hash function.

T          F          6.  The cryptographic hash function is not a versatile cryptographic

algorithm.

T          F          7.  It is possible to use a hash function but no encryption for message

authentication.

T          F          8.  Encryption hardware is optimized toward smaller data sizes.

T          F          9.  Hash functions are commonly used to create a one-way password

file.

T          F          10. A weak hash function is sufficient to protect against an attack in

which one party generates a message for another party to sign.

T          F          11. The way to measure the resistance of a hash algorithm to

cryptanalysis is to compare its strength to the effort required for a

brute-force attack.

T          F          12. It can be shown that some form of birthday attack will succeed

against any hash scheme involving the use of cipher block

chaining without a secret key, provided that either the resulting

hash code is small enough or that a larger hash code can be

decomposed into independent subcodes.

T          F          13. The most widely used hash function has been the Whirlpool.

T          F          14. Big-endian format is the most significant byte of a word in the

T          F          15. The SHA-512 algorithm has the property that every bit of the hash

code is a function of every bit of the input.

MULTIPLE CHOICE

1. The principal object of a hash function is __________ .

1. data integrity B.  compression

1. collision resistance D.  mapping messages

1. A ___________ accepts a variable length block of data as input and produces a fixed size hash value h = H(M).

1. hash resistance B.  hash value

1. hash function D.  hash code

1. The Secure Hash Algorithm design closely models, and is based on, the hash function __________ .

1. MD5 B.  FIPS 180

1. RFC 4634 D.  MD4

1. A ___________ is an algorithm for which it is computationally infeasible to find either (a) a data object that maps to a pre-specified hash result or (b) two data objects that map to the same hash result.

1. cryptographic hash function B.  strong collision resistance

1. one-way hash function D.  compression function

1. The cryptographic hash function requirement that guarantees that it is impossible to find an alternative message with the same hash value as a given message and prevents forgery when an encrypted hash code is used is the ___________ .

1. collision resistant B.  pseudorandomness

1. preimage resistant D.  second preimage resistant

1. __________ is a mechanism or service used to verify the integrity of a message.

1. Message authentication B.  Data compression

1. Data mapping D.   Message digest

1. Message authentication is achieved using a __________ .

1. DES B.  MDF

1. SHA D.  MAC

1. __________ are measures of the number of potential collisions for a given hash value.

1. MACs             B.  Primitives

1. Hash codes D.  Preimages

1. A hash function that satisfies the properties of variable input size, fixed output size, efficiency, preimage resistant and second preimage resistant is referred to as a __________.

1. strong hash function B.  collision resistant function

1. weak hash function D.  preimage resistant function

1. The effort required for a collision resistant attack is explained by a mathematical result referred to as the ___________ .

1. hash value D.  message authentication code

1. An ideal hash algorithm will require a cryptanalytic effort __________ the brute-force effort.

1. less than or equal to B.  greater than or equal to

1. less than             D.  greater than

1. The Secure Hash Algorithm was developed by the ___________ .

1. ITIL B.  IEEE

1. ISO             D.  NIST

1. SHA-1 produces a hash value of __________ bits.

1. 224 B.  160

1. 384 D.  256

1. Given a hash function H, with n possible outputs and a specific value H(x), if H is applied to k random inputs, what must be the value of k so that the probability that at least one input y satisfies H(y) = H(x) is 0.5? is a reference to the __________ .

1. authentication code B.  collision resistant

1. big endian             D.  birthday attack

1. Three new versions of SHA with hash value lengths of 256, 384, and 512 bits are collectively known as __________ .

1. SHA-3 B.  SHA-1

1. SHA-2 D.  SHA-0

1. The compression function used in secure hash algorithms falls into one of two categories: a function specifically designed for the hash function or an algorithm based on a ___________ .

1. A __________ is an attack based on weaknesses in a particular cryptographic algorithm.

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