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Example of a Key Derivation Function chain as used in the Signal Protocol.The output of one KDF function is the input to the next KDF function in the chain. In cryptography, a key derivation function (KDF) is a cryptographic algorithm that derives one or more secret keys from a secret value such as a master key, a password, or a passphrase using a pseudorandom function (which typically uses a ...
Mask generation functions, as generalizations of hash functions, are useful wherever hash functions are. However, use of a MGF is desirable in cases where a fixed-size hash would be inadequate. Examples include generating padding, producing one-time pads or keystreams in symmetric-key encryption, and yielding outputs for pseudorandom number ...
HKDF-Extract takes "input key material" (IKM) such as a shared secret generated using Diffie-Hellman, and an optional salt, and generates a cryptographic key called the PRK ("pseudorandom key"). This acts as a "randomness extractor", taking a potentially non-uniform value of high min-entropy and generating a value indistinguishable from a ...
Password is the master password from which a derived key is generated; Salt is a sequence of bits, known as a cryptographic salt; c is the number of iterations desired; dkLen is the desired bit-length of the derived key; DK is the generated derived key; Each hLen-bit block T i of derived key DK, is computed as follows (with + marking string ...
If the key is random and is at least as long as the message, the XOR cipher is much more secure than when there is key repetition within a message. [4] When the keystream is generated by a pseudo-random number generator, the result is a stream cipher. With a key that is truly random, the result is a one-time pad, which is unbreakable in theory.
For this description, the following functions and operators are used: Head (data, a): returns the first a bits of the 'data' string. Tail (data, a): returns the last a bits of the 'data' string. Encrypt (K, data): use the underlying block cipher in encrypt mode on the 'data' string using the key K.
The sponge construction for hash functions. P i are blocks of the input string, Z i are hashed output blocks.. In cryptography, a sponge function or sponge construction is any of a class of algorithms with finite internal state that take an input bit stream of any length and produce an output bit stream of any desired length.
Key stretching algorithms depend on an algorithm which receives an input key and then expends considerable effort to generate a stretched cipher (called an enhanced key [citation needed]) mimicking randomness and longer key length. The algorithm must have no known shortcut, so the most efficient way to relate the input and cipher is to repeat ...