Cryptography Extra 5 Flashcards
fixed size input that is random or pseudo-random, called a nonce and increases randomness of result cipher text.
IV
uses identically for encrypt/decrypt as a data stream, is XORed w/key. key length from 1-2048 bytes; the key constitutes a state table used for subsequent generation of pseudo-random bytes and then to generate a pseudo-random stream which is XORed with the plaintext to produce the ciphertext.
RC4 (symmetric stream cipher)
MD5 is not collision resistant.
FORK-256 (hash function) : uses 512 blocks.
RIPEMD (hash function) : 160-bit hash
GOST (hash) : 256-bits
Tiger (hash) : 192-bits
*** EC : formula -> y^2 = x^3 + Ax + B
hash info Etc …
adds key to hash to improve integrity, MAC uses a block cipher in CBC mode to improve integrity.
*** Bob gets alices public key, bob encrypts alices public key, bob sends message to alice, alice decrypts message with her private key.
HMAC / MAC Etc …
having changes to one character in the plaintext affect multiple characters in the ciphertext.
Diffusion
attempts to make the relationship between the statistical frequencies of the ciphertext and the actual key as complex as possible. This occurs by using a complex substitution algorithm.
Confusion
Avalanche : a small change yields large effects to the output.
Entropy : measure of uncertainty associated w/a random variable.
info
contains a public key and some means to verify whose public key it is.
Digital Certificate
It is a digital document that contains a public key signed by the trusted third party, which is known as a Certificate Authority, or CA.
X.509
The primary role of the CA is to digitally sign and publish the public key bound to a given user. It is an entity trusted by one or more users to manage certificates.
CA
