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CRYPTOGRAPHY 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 ✔✔D The most widely used asymmetric encryption algorithm is what? A RSA B Vigenere C DES D Caesar Cipher ✔✔A Original, unencrypted information is referred to as ____. A text B plaintext C cleantext D ciphertext ✔✔B Which of the following is NOT an asymmetric system? A PGP B RSA
C SSL
D DES ✔✔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 ✔✔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 ✔✔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 ✔✔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 64 bits ✔✔A Which of the following is NOT a key size used by AES? A 512 bits B 128 bits C 192 bits D 256 bits ✔✔A Which of the following was a multi alphabet cipher widely used from the 16th century (15 53 ) to the early 20 th century (1900s)? A Vigenere B Caesar C Atbash D Scytale ✔✔A Which of the following is a substitution cipher used by ancient Hebrew scholars? A Caesar B Vigenere C Scytale D Atbash ✔✔D Shifting each letter in the alphabet a fixed number of spaces to the right or left is an example of what? A Bit shifting B Confusion C Multi substitution
D Single substitution ✔✔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 ✔✔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. ✔✔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 ✔✔B ____ was designed to provide built in cryptography for the clipper chip. A Blowfish B Skipjack C GOST
D Cipher feedback (CFB) ✔✔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) ✔✔C This is a method for turning a block cipher into a stream cipher by generating a keystream block, which are then XORed with the plaintext blocks to get the ciphertext. A Cipher feedback (CFB) B Electronic codebook (ECB) C Output feedback (OFB) D Cipher-block chaining (CBC) ✔✔C Which of the following modes can be used to turn a block cipher into a stream cipher? A Propagating cipher-block chaining (PCBC) and Electronic codebook (ECB) B Counter Mode (CTR) and Propagating cipher-block chaining (PCBC) C Electronic codebook (ECB) and Output feedback (OFB) D Output feedback (OFB) and Counter Mode (CTR) ✔✔D A fixed-size pseudorandom number that is fed into a symmetric cipher to increase randomness is called what?
A IV
B Key C Chain D Salt ✔✔A A number that is used only one time then discarded is called what? A Nonce B Chain C Salt D IV ✔✔A Which of the following is a stream cipher that uses variable length key from 1 to 256 bytes? A RC B AES C DESx D DES ✔✔A This algorithm was published by the German engineering firm Seimans in 1993. 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 ✔✔C Which of the following is NOT required for a hash? A Minimum key length of 256 bits
A 256
B 128
C 512
D 64 ✔✔C
In 1977 researchers at MIT described what asymmetric algorithm? A RSA B AES C DH D EC ✔✔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 ✔✔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 ) ✔✔C U.S. Patent 5,231,668 and FIPS 186 define what algorithm? A AES B RSA C Elliptic Curve (EC)
D Digital Signature Algorithm (DSA) ✔✔D What is X.50 9? A The standard for PGP certificates B The standard for encrypting email C The standard for FIPS 186 D The standard for digital certificates ✔✔D What is contained in a CRL? A Keys for RSA B New certificates C Revoked certificates D Keys for AES ✔✔C What does the Online Certificate Status Protocol (OCSP) provide? A Revoked certificates B Hashing C VPN connectivity D Encryption ✔✔A In terms of cryptanalysis, what does it mean to break a cipher? A finding a method to decrypt a message that is at least twice as efficient as brute force B trying every possible key until you can decrypt the message C deploying an algorithm that uses a 228 bit key
D Shamir's principle ✔✔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 ✔✔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 ✔✔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. ✔✔C What does the OCSP protocol provide? A encryption B VPN connectivity C hashing D a real time protocol for verifying certificates ✔✔D
U.S. encryption standard that replaced DES. Block symmetric cipher that uses 128 - bit block sizes and various key lengths (128, 192, 256). ✔✔AES DES, 3DES, SHA, AES (some AES implementations are Type I) ✔✔Class 3 Algorithms Encryption method where the sender and receiver use an instance of the same key for encryption and decryption purposes. ✔✔Symmetric Block symmetric algorithm chosen by NIST as an encryption standard in 1976. It uses a 56 - bit true key bit size, 64 - bit block size, and 16 rounds of computation. ✔✔Data Encryption Standard (DES) technical specification indicating how multimedia data and e-mail binary attachments are to be transferred. ✔✔Multipurpose Internet Mail Extensions (MIME) Valid data transmission is maliciously or fraudulently repeated to allow an entity gain unauthorized access. ✔✔Replay Attack protocol suite provides a method of setting up a secure channel for protected data exchange between two devices. ✔✔Internet Protocol Security (IPSec) Juniper (block cipher) MAYFLY (asymmetric) FASTHASH (hashing) WALBURN (high bandwith link encryption) PEGASUS (satellite telemetry) ✔✔Class 1 Algorithms Component of a PKI that creates and maintains digital certificates throughout their life cycles. ✔✔Certificate Authority
Cryptanalysis attack where the attacker is assumed to have access to sets of corresponding plaintext and ciphertext. ✔✔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. ✔✔Online Certificate Status Protocol (OCSP) What is the formula Me%n related to? ✔✔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 ✔✔P= E(k,c) Symmetric decryption Not certified for government use ✔✔Class 4 algorithms 64 bit algorithm operating at 56 bits with an 8 bit parity block ✔✔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. ✔✔Authentication Header (AH) and Encapsulating Security Payload (ESP). developed as a Russian national standard and produced fixed length outputs of 256 bits ✔✔GOST A measure of the uncertainty associated with a random variable ✔✔Entropy Attempts to make the statistical frequencies of the ciphertext and actual key as complex as possible ✔✔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. ✔✔Serpent What is the difference between Secure HTTP (SHTTP) and HTTP Secure (HTTPS)? ✔✔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 1 6th century to the early 20th century? ✔✔Vigenere A _____ is a function that takes a variable-size input m and returns a fixed-size string. ✔✔Hash A small change that yields large effects in the output. ✔✔Avalanche Private organizations or governmental security ✔✔Class 5 Certificates Numbers that have no factors in common with another. ✔✔Co-prime numbers Cryptanalysis attack that exploits vulnerabilities within the intrinsic algebraic structure of mathematical functions. ✔✔Algebraic attack Designed by Ross Anderson and Eli Biham in 199 5. The size of a ________ hash value is 192 bits. ✔✔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? ✔✔User B's public key Public key algorithm that can be used for digital signatures, encryption, and key exchange.
It should be impossible for any attacker to calculate, or guess from an inner state of the generator, any previous numbers in the sequence or any previous inner generator states ✔✔BSI criteria K states: 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. ✔✔Skipjack Algorithm that was chosen for the Data Encryption Standard, which was altered and renamed Data Encryption Algorithm. ✔✔Lucifer Announced by NIST as FIPS 197. Has 3 key sizes: 128, 192, 256 and all operate on 128 bit block ✔✔AES Symmetric cipher that applies DES three times to each block of data during the encryption process. ✔✔Triple DES (3DES) Attack that uses information (timing, power consumption) that has been gathered to uncover sensitive data or processing functions. ✔✔Side-channel attack A 160 bit hash with 3 other versions: RIPEMD- 128 (128 bit), RIPEMD- 256 (256 bit), RIPEMD- 320 (320 bit) ✔✔RIPEMD- 160 Transposition processes used in encryption functions to increase randomness. ✔✔Diffusion Used to store, distribute, and maintain cryptographic session and secret keys. ✔✔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. ✔✔Pretty Good Privacy (PGP) A number that is used only one time then discarded is called what? ✔✔Nonce Improvement on FISH due to vulnerability to known-plaintext attacks. Published by Ross Anderson. ✔✔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 P 1363 ✔✔MQV A cryptographic protocol and infrastructure developed to send encrypted credit card numbers over the Internet. ✔✔Secure Electronic Transaction (SET) The algorithm is used identically for encryption and decryption as the data stream is simply XORed with the key. RC 4 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 ✔✔RC 4 The payload and the routing and header information are protected in this mode. ✔✔Tunnel mode Values that are used with algorithms to increase randomness for cryptographic functions. ✔✔Initialization vectors (IVs) Ticket granting service ✔✔TGS This is a variation of DES that XORs another 6 4 - bit key to the plaintext before applying the DES algorithm.
