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The Secure Hash Algorithms are a family of cryptographic hash functions published by the National Institute of Standards and Technology (NIST) as a U.S. Federal Information Processing Standard (FIPS), including: SHA-0: A retronym applied to the original version of the 160-bit hash function published in 1993 under the name "SHA". It was ...
The signature schemes are actually signatures with appendix, which means that rather than signing some input data directly, a hash function is used first to produce an intermediary representation of the data, and then the result of the hash is signed. This technique is almost always used with RSA because the amount of data that can be directly ...
crypt is a POSIX C library function. It is typically used to compute the hash of user account passwords. The function outputs a text string which also encodes the salt (usually the first two characters are the salt itself and the rest is the hashed result), and identifies the hash algorithm used (defaulting to the "traditional" one explained below).
Hash-based signature schemes use one-time signature schemes as their building block. A given one-time signing key can only be used to sign a single message securely. Indeed, signatures reveal part of the signing key. The security of (hash-based) one-time signature schemes relies exclusively on the security of an underlying hash function.
SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. [ 3 ] [ 4 ] They are built using the Merkle–Damgård construction , from a one-way compression function itself built using the Davies–Meyer structure from a specialized block cipher.
E.g., an attacker who wants to know the decryption of a ciphertext c ≡ m e (mod n) may ask the holder of the private key d to decrypt an unsuspicious-looking ciphertext c′ ≡ cr e (mod n) for some value r chosen by the attacker. Because of the multiplicative property, c ' is the encryption of mr (mod n).
Standard algorithms and protocols provide a focus for study; standards for popular applications attract a large amount of cryptanalysis. Encryption standards [ edit ]
The Digital Signature Algorithm (DSA) is a public-key cryptosystem and Federal Information Processing Standard for digital signatures, based on the mathematical concept of modular exponentiation and the discrete logarithm problem. In a public-key cryptosystem, a pair of private and public keys are created: data encrypted with either key can ...