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C839 - Intro to Cryptography final
Questions and Answers)
What type of encryption uses different keys to encrypt and decrypt the message? A Symmetric B Private key C Secure D Asymmetric - Solution D The most widely used asymmetric encryption algorithm is what? A RSA B Vigenere C DES D Caesar Cipher - Solution A Original, unencrypted information is referred to as ____. A text B plaintext C cleantext D ciphertext - Solution B Which of the following is NOT an asymmetric system? A PGP B RSA C SSL D DES - Solution D In order for User A to send User B an encrypted message that only User B can read, User A must encrypt message with which of the following keys? A User A's public key B User A's private key
C User B's public key D User B's private key - Solution C The greatest weakness with symmetric algorithms is _____. A They are less secure than asymmetric B The problem of key exchange C They are slower than asymmetric D The problem of generating keys - Solution B Which of the following is generally true about block sizes? A Smaller block sizes increase security B Block sizes must be more than 256 bits to be secure C Block size is irrelevant to security D Larger block sizes increase security - Solution D A _____ is a function that takes a variable-size input m and returns a fixed- size string. A Symmetric cipher B Hash C Asymmetric cipher D Feistel - Solution B Which of the following is a cryptographic protocol that allows two parties to establish a shared key over an insecure channel? A Elliptic Curve B RSA C MD D Diffie-Hellman - Solution D A _________ is a digital representation of information that identifies you as a relevant entity by a trusted third party? A Digital Signature B Hash C Ownership stamp D Digest - Solution A
A Bit shifting B Confusion C Multi substitution D Single substitution - Solution D Which of the following most accurately defines encryption? A changing a message so it can only be easily read by the intended recipient B Making binary changes to a message to conceal it C changing a message using complex mathematics D Applying keys to plain text - Solution A If you use substitution alone, what weakness is present in the resulting cipher text? A It is the same length as the original text B It is easily broken with modern computers. C It is too simple. D Because it maintains letter and word frequency. - Solution D _____ uses at least two different shifts, changing the shift with different letters in the plain text. A Atbash B multi-alphabet encryption C Scytale D Caesar cipher - Solution B ____ was designed to provide built in cryptography for the clipper chip. A Blowfish B Skipjack C GOST D 3DES - Solution B
Which of the following uses an 80 bit key on 64 bit blocks? A Twofish B AES C Skipjack D DES - Solution C With _____, the message is divided into blocks and each block is encrypted separately. This is the most basic mode for symmetric encryption. A Electronic codebook (ECB) B Cipher-block chaining (CBC) C Cipher feedback (CFB) D Output feedback (OFB) - Solution A Which of the following is an example of an unbalanced Feistel? A 3DES B Skipjack C Twofish D AES - Solution B This process is done by having each block of plaintext is XORed with the previous ciphertext block before being encrypted. A Output feedback (OFB) B Cipher-block chaining (CBC) C Electronic codebook (ECB) D Cipher feedback (CFB) - Solution B The process wherein the ciphertext block is encrypted then the ciphertext produced is XOR'd back with the plaintext to produce the current ciphertext block is called what? A Output feedback (OFB) B Cipher-block chaining (CBC) C Cipher feedback (CFB) D Electronic codebook (ECB) - Solution C
B AES
C DESx D DES - Solution A This algorithm was published by the German engineering firm Seimans in
- It is a software based stream cipher using Lagged Fibonacci generator along with a concept borrowed from the shrinking generator ciphers. A RC B Blowfish C FISH D Twofish - Solution C Which of the following is NOT required for a hash? A Minimum key length of 256 bits B Variable-length input, fixed-length output C Non-reversible D Few collisions - Solution A A ______ refers to a situation where two different inputs yield the same output. A Substitution B Convergence C Collision D Transposition - Solution C What is a salt? A Key rotation B Random bits intermixed with a hash to increase randomness and reduce collisions. C Random bits intermixed with a symmetric cipher to increase randomness and make it more secure. D Key whitening - Solution B
RFC 1321 describes what hash? A RIPEMD B SHA C GOST D MD5 - Solution D What size block does FORK256 use? A 256 B 128 C 512 D 64 - Solution C In 1977 researchers at MIT described what asymmetric algorithm? A RSA B AES C DH D EC - Solution A What is the formula (M^e)(%n) related to? A Encrypting with EC B Generating Mersenne primes C Decrypting with RSA D Encrypting with RSA - Solution C Which of the following equations is related to EC? A P = Cd%n B Me%n C y2 = x3 + Ax + B D Let m = (p-1)(q-1) - Solution C U.S. Patent 5,231,668 and FIPS 186 define what algorithm? A AES B RSA
B CHAP
C SPAP
D EAP - Solution B What is a TGS? A The server that grants Kerberos tickets B protocol for encryption C protocol for key exchange D The server that escrows keys - Solution A What is Kerchoff's principle? A A minimum key size of 256 bits is necessary for security. B Both algorithm and key should be kept secret. C A minimum of 15 rounds is needed for a Feistel cipher to be secure. D Only the key needs to be secret, not the actual algorithm. - Solution D Which of the following is a fundamental principle of cryptography that holds that the algorithm can be publically disclosed without damaging security? A Babbage's principle B Kerkchoff's principle C Vigenere's principle D Shamir's principle - Solution B A process that puts a message into the least significant bits of a binary file is called what? A Symmetric cryptography B Masking C Steganography D Asymmetric cryptography - Solution C If you wished to see a list of revoked certificates from a CA, where would you look? A CRL B CA C RFC
D RA - Solution A Which of the following is generally true about block ciphers? A Secret block ciphers should be trusted. B Block ciphers permute the bits of the input plaintext. C The plaintext and ciphertext are always the same size. D A block cipher is an encryption function for variable-size blocks of data. - Solution C What does the OCSP protocol provide? A encryption B VPN connectivity C hashing D a real time protocol for verifying certificates - Solution D U.S. encryption standard that replaced DES. Block symmetric cipher that uses 128-bit block sizes and various key lengths (128, 192, 256). - Solution AES DES, 3DES, SHA, AES (some AES implementations are Type I) - Solution Class 3 Algorithms Encryption method where the sender and receiver use an instance of the same key for encryption and decryption purposes. - Solution Symmetric Block symmetric algorithm chosen by NIST as an encryption standard in
- It uses a 56-bit true key bit size, 64-bit block size, and 16 rounds of computation. - Solution Data Encryption Standard (DES) technical specification indicating how multimedia data and e-mail binary attachments are to be transferred. - Solution Multipurpose Internet Mail Extensions (MIME) Valid data transmission is maliciously or fraudulently repeated to allow an entity gain unauthorized access. - Solution Replay Attack
individuals, and intended for email - Solution Class 1 Certificates A form of cryptanalysis applicable to symmetric key algorithms that was invented by Eli Biham and Adi Shamir. The examination of differences in an input and how that affects the resultant difference in the output. - Solution Differential cryptanalysis Cryptanalysis attack where the attacker is assumed to have access to sets of corresponding plaintext and ciphertext. - Solution Known plaintext attack Carries out real-time validation of a certificate and reports back to the user whether the certificate is valid, invalid, or unknown. OCSP checks the CRL that is maintained by the CA. - Solution Online Certificate Status Protocol (OCSP) What is the formula Me%n related to? - Solution Encrypting with RSA Plain-text is equal to the encryption function (E) with the key (k) and the ciphertext (c) being passed as parameters to that function - Solution P= E(k,c) Symmetric decryption Not certified for government use - Solution Class 4 algorithms 64 bit algorithm operating at 56 bits with an 8 bit parity block - Solution DES AH is the authenticating protocol, and ESP is an authenticating and encrypting protocol that uses cryptographic mechanisms to provide source authentication, confidentiality, and message integrity. - Solution Authentication Header (AH) and Encapsulating Security Payload (ESP). developed as a Russian national standard and produced fixed length outputs of 256 bits - Solution GOST A measure of the uncertainty associated with a random variable - Solution Entropy
Attempts to make the statistical frequencies of the ciphertext and actual key as complex as possible - Solution Confusion Like AES, Serpent has a block size of 128 bits and can have a key size of 128, 192, or 256 bits. The algorithm is also a substitution-permutation network like AES. It uses 32 rounds working with a block of four 32-bit words. Each round applies one of eight 4-bit to 4-bit S-boxes 32 times in parallel. Designed by Ross Anderson, Eli Biham, and Lars Knudsen. - Solution Serpent What is the difference between Secure HTTP (SHTTP) and HTTP Secure (HTTPS)? - Solution S-HTTP is a technology that protects each message sent between two computers, while HTTPS protects the communication channel between two computers, messages and all. Which of the following was a multi alphabet cipher widely used from the 16th century to the early 20th century? - Solution Vigenere A _____ is a function that takes a variable-size input m and returns a fixed- size string. - Solution Hash A small change that yields large effects in the output. - Solution Avalanche Private organizations or governmental security - Solution Class 5 Certificates Numbers that have no factors in common with another. - Solution Co- prime numbers Cryptanalysis attack that exploits vulnerabilities within the intrinsic algebraic structure of mathematical functions. - Solution Algebraic attack Designed by Ross Anderson and Eli Biham in 1995. The size of a ________ hash value is 192 bits. - Solution TIGER In order for User A to send User B an encrypted message that only User B can read, User A must encrypt message with which of the following keys? - Solution User B's public key
Developed by the NSA for use in the clipper chip. Skipjack uses an 80-bit key to encrypt or decrypt 64-bit data blocks. It is an unbalanced Feistel network with 32 rounds. - Solution Skipjack Algorithm that was chosen for the Data Encryption Standard, which was altered and renamed Data Encryption Algorithm. - Solution Lucifer Announced by NIST as FIPS 197. Has 3 key sizes: 128, 192, 256 and all operate on 128 bit block - Solution AES Symmetric cipher that applies DES three times to each block of data during the encryption process. - Solution Triple DES (3DES) Attack that uses information (timing, power consumption) that has been gathered to uncover sensitive data or processing functions. - Solution Side-channel attack A 160 bit hash with 3 other versions: RIPEMD-128 (128 bit), RIPEMD- (256 bit), RIPEMD-320 (320 bit) - Solution RIPEMD- Transposition processes used in encryption functions to increase randomness. - Solution Diffusion Used to store, distribute, and maintain cryptographic session and secret keys. - Solution Key Distribution Center (KDC) Designed by Phil Zimmerman as a freeware e-mail security program and was released in 1991. It was the first widespread public key encryption program. - Solution Pretty Good Privacy (PGP) A number that is used only one time then discarded is called what? - Solution Nonce Improvement on FISH due to vulnerability to known-plaintext attacks. Published by Ross Anderson. - Solution PIKE
Stands for Menezes-Qu-Vanstone and is a protocol used for key agreement that is based on DH. Incorporated in public key standard IEEE P1363 - Solution MQV A cryptographic protocol and infrastructure developed to send encrypted credit card numbers over the Internet. - Solution Secure Electronic Transaction (SET) The algorithm is used identically for encryption and decryption as the data stream is simply XORed with the key. RC4 uses a variable-length key from 1 to 2048 bits, (minimum of 40 bits or higher to be considered secure). That key constitutes a state table that is used for the subsequent generation of pseudo-random bytes and then to generate - Solution RC The payload and the routing and header information are protected in this mode. - Solution Tunnel mode Values that are used with algorithms to increase randomness for cryptographic functions. - Solution Initialization vectors (IVs) Ticket granting service - Solution TGS This is a variation of DES that XORs another 64-bit key to the plaintext before applying the DES algorithm. The concept of simply XORing in an additional key is called whitening. This adds to the confusion of the resultant text. - Solution DESx The total number of co prime numbers for a number n - Solution Euler's Totient Naor-Reingold, Mersenne Twister, Linear Congruential Generator, Lehmer Random Number Generator (twisted generalized feedback shift registers), Lagged Fibonacci Generator (LFG) - Solution Examples of PRNGs (pseudo random number generators)
A message is input into a hash function. Then the hash value is encrypted using the private key of the sender. The result of these two steps yields a __________________. - Solution Digital Signature A 16-round Feistel cipher working on 64-bit blocks. Unlike DES, it can have varying key sizes ranging from 32 bits to 448 bits. Designed by Bruce Schneier. - Solution Blowfish Which of the following modes can be used to turn a block cipher into a stream cipher? - Solution Output feedback (OFB) and Counter Mode (CTR) Online business transactions between companies - Solution Class 4 certificates EFS is encryption for files while Bitlocker is used for full disk encryption - Solution EFS vs. Bitlocker Cryptanalysis attack that exploits vulnerabilities within the algorithm structure. - Solution Analytic attack Open-community and standardized version of SSL but TLS is more extensible and is backward compatible with SSL. - Solution Transport-Layer Security (TLS) Uses a block size of 128 bits and key sizes up to 256 bits. It is a Feistel cipher. Designed by Bruce Schneier, John Kelsey, Doug Whiting, David Wagner, Chris Hall, and Niels Ferguson. - Solution Twofish 160 bit hash - Solution SHA- Cryptographic attack that exploits the mathematics behind the birthday problem in the probability theory forces collisions within hashing functions. - Solution Birthday attack A process that puts a message into the least significant bits of a binary file is called what? - Solution Steganography
Cryptanalysis attack that tries to uncover a mathematical problem from two different ends. - Solution Meet-in-the-middle attack Asymmetric encryption method developed in 1984. It is used in PGP implementations and GNU Privacy Guard Software. Consists of 3 parts: key generator, encryption algorithm, and decryption algorithm. - Solution El Gamal A combination of the ISAKMP and OAKLEY protocols. - Solution Internet Key Exchange (IKE) The payload of the message is protected - Solution Transport mode What did WPA replace RC4 with? - Solution TKIP (Temporal Key Integrity Protocol) N denotes natural numbers. These are also sometimes called the counting numbers. They are 1, 2, 3, etc. Z denotes the integers. These are whole numbers such as -1, 0, 1, 2, etc. Basically, this set is the natural numbers combined with zero and the negative numbers. Q denotes rational numbers (or the ratios of integers). They are any number that can be expressed as a ratio of two integers. Examples are 3/2, 17/4, and 1/5. R denotes real numbers. This includes the rational number as well as numbers that cannot be expressed as a ratio of two integers, such as 2/3. i denotes imaginary numbers. These are numbers whose square is a negative. For example, √-1 = 1i. - Solution Explain the number groupings: N, Z, Q, R, i An encryption function for fixed-size blocks of data. The current generation has a block size of 128 bits (16 bytes). - Solution block cipher To encrypt with a block cipher, we need a ___________. - Solution secret key
