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Stream cipher. The operation of the keystream generator in A5/1, an LFSR-based stream cipher used to encrypt mobile phone conversations. A stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream ( keystream ). In a stream cipher, each plaintext digit is encrypted one at a time with the ...
Keystream. In cryptography, a keystream is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted message (the ciphertext). The "characters" in the keystream can be bits, bytes, numbers or actual characters like A-Z depending on the usage case. Usually each character in the keystream is ...
RC4 was designed by Ron Rivest of RSA Security in 1987. While it is officially termed "Rivest Cipher 4", the RC acronym is alternatively understood to stand for "Ron's Code" [9] (see also RC2, RC5 and RC6 ). RC4 was initially a trade secret, but in September 1994, a description of it was anonymously posted to the Cypherpunks mailing list. [10]
Stream ciphers are vulnerable to attack if the same key is used twice (depth of two) or more. Say we send messages A and B of the same length, both encrypted using same key, K. The stream cipher produces a string of bits C (K) the same length as the messages. The encrypted versions of the messages then are: where xor is performed bit by bit.
FIREFLY key - (NSA) keys used in an NSA system based on public key cryptography. key encryption key (KEK) - key used to protect MEK keys (or DEK/TEK if MEK is not used). key production key (KPK) -Key used to initialize a keystream generator for the production of other electronically generated keys.
On the other hand, the generation of a master key requires a higher quality, such as more entropy. And in the case of one-time pads, the information-theoretic guarantee of perfect secrecy only holds if the key material comes from a true random source with high entropy, and thus any kind of pseudorandom number generator is insufficient.
A pseudorandom number generator ( PRNG ), also known as a deterministic random bit generator ( DRBG ), [1] is an algorithm for generating a sequence of numbers whose properties approximate the properties of sequences of random numbers. The PRNG-generated sequence is not truly random, because it is completely determined by an initial value ...
Block cipher. In cryptography, a block cipher is a deterministic algorithm that operates on fixed-length groups of bits, called blocks. Block ciphers are the elementary building blocks of many cryptographic protocols. They are ubiquitous in the storage and exchange of data, where such data is secured and authenticated via encryption .