FIPS-PUB-180-3

Abstract

<strong>INTRODUCTION</strong> <br>This Standard specifies five secure hash algorithms, SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512. All five of the algorithms are iterative, one-way hash functions that can process a message to produce a condensed representation called a message digest. These algorithms enable the determination of a message's integrity: any change to the message will, with a very high probability, result in a different message digest. This property is useful in the generation and verification of digital signatures and message authentication codes, and in the generation of random numbers or bits. <br>Each algorithm can be described in two stages: preprocessing and hash computation. Preprocessing involves padding a message, parsing the padded message into m-bit blocks, and setting initialization values to be used in the hash computation. The hash computation generates a message schedule from the padded message and uses that schedule, along with functions, constants, and word operations to iteratively generate a series of hash values. The final hash value generated by the hash computation is used to determine the message digest. <br>The five algorithms differ most significantly in the security strengths that are provided for the data being hashed. The security strengths of these five hash functions and the system as a whole when each of them is used with other cryptographic algorithms, such as digital signature algorithms and keyed-hash message authentication codes, can be found in [SP 800-57] and [SP 800-107].