C839 Additional Study PDF

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Summary

COMMON SYMMETRIC BLOCK CIPHERSNAME BLOCKSIZEKEY SIZE ROUNDS STRUCTUREDES 64 bit 56 bit 16 rounds Feistel AES 128 bit 128, 192, or 256 bit10, 12, or 14 rounds Substitution- permutation matrix Blowfish 64 bit 32-448 bit 16 rounds Feistel Twofish 128 bit 1-256 bit 16 rounds Feistel Serpent 128 bit 128,...

Description

COMMON SYMMETRIC BLOCK CIPHERS NAME DES AES

BLOCK SIZE 64 bit 128 bit

Blowfish Twofish

64 bit 128 bit

Serpent

128 bit

Skipjack IDEA

64 bit 64 bit

KEY SIZE

ROUNDS

STRUCTURE

56 bit 128, 192, or 256 bit 32-448 bit 1-256 bit

16 rounds 10, 12, or 14 rounds

Feistel Substitutionpermutation matrix Feistel Feistel

128, 192, or 256 bit 80 bit 128 bit

32 rounds

16 rounds 16 rounds

32 rounds 8.5 rounds

Substitutionpermutation matrix Unbalanced Feistel Lai-Massey Scheme

COMMON SYMMETRIC STREAM CIPHERS NAME RC4

NOTABLE ATTRIBUTE 2064 bit state size, 1-2048 bit key size (40 bit minimum recommended), 1 round Uses Lagged Fibonacci pseudorandom number generator

FISH PIKE

Revised version of FISH to address known plaintext attack vulnerabilities

COMMON ASYMMETRIC ENCRYPTION ALGORITHMS NAME

NOTABLE ATTRIBUTE

RSA ECC

Leverages prime number characteristics, 1024-4096 bit variable key size, 1 round Leverages discrete logarithm characteristics

El Gamal

Used in recent versions of PGP

DSA

A Federal Information Processing Standard for digital signatures (FIPS 186)

NAME

HASH VALUE

MD5 SHA1 SHA256 FORK256 GOST TIGER

128 bit 160 bit 256 bit 256 bit 256 bit 192 bit

NAME RSA EC SYMMETRIC DECRYPTIO N SYMMETRIC ENCRYPTIO N

FORMULA Me % n y2 = x3 + Ax + B

P = E(k,c)

C

E(k p)

Cryptanalysis is the art or process of deciphering coded messages without being told the key. Frequency Analysis: examining ciphertext looking for patterns that can be examined against the frequency rate of letter usage by language. Kasiski test: A variation on frequency analysis that is used to attack polyalphabetic substitution ciphers. Chosen Plaintext Attack: attacker obtains the ciphertexts corresponding to a set of plaintexts. This can allow the attacker to attempt to derive the key used and thus decrypt other messages encrypted with that key. Ciphertext Only Attack: attacker ONLY has access to the ciphertext of messages. Related-Key Attack: Similar to the Chosen Plaintext Attack, except that the attacker is able to get messages encrypted with two different keys (the keys need to be related, meaning that one was derived from the other as is the case in wireless systems) Linear Cryptanalysis: a known plaintext attack and uses a linear approximation to describe the behavior of the block cipher. Given sufficient pairs of plaintext and corresponding ciphertext, bits of information about the key can be obtained and increased amounts of data will usually give a higher probability of success. Invented by Mitsarue Matsui.

Differential Cryptanalysis: a form of cryptanalysis applicable to symmetric key algorithms. This 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. Integral Cryptanalysis: Similar to Differential Cryptanalysis but uses a different technique. Uses sets or even multisets of chosen plaintexts of which part is held constant and another part varies through all possibilities. How do we measure success? • Total break - attacker gets the key. • Global deduction - attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key. • Instance (local) deduction - attacker discovers additional plaintexts (or ciphertexts) not previously known. • Information deduction - attacker gains some information about plaintexts (or ciphertexts) not previously known. • Distinguishing algorithm - attacker can distinguish the cipher from a random permutation...