RadioGatún

RadioGatún is a cryptographic hash primitive created by Guido Bertoni, Joan Daemen, Michaël Peeters, and Gilles Van Assche. It was first publicly presented at the NIST Second Cryptographic Hash Workshop, held in Santa Barbara, California, on August 24–25, 2006, as part of the NIST hash function competition.

Although RadioGatún is a derivative of Panama, a stream cipher and hash construction from the late 1990s whose hash construction has been broken, RadioGatún does not have Panama's weaknesses when used as a hash function.

RadioGatún is actually a family of 64 different hash functions, distinguished by a single parameter, the word width in bits (w), adjustable between 1 and 64. The algorithm uses 58 words, each of size w, to store its internal state. Thus, for example, the 32-bit version needs 232 bytes to store its state and the 64-bit version 464 bytes.

RadioGatún can be used either as a hash function or a stream cipher; it can output an arbitrarily long stream of pseudo-random numbers.

The same team that developed RadioGatún went on to make considerable revisions to this cryptographic primitive, leading to the Keccak SHA-3 submission.

The algorithm's designers, in the original RadioGatún paper, claimed that the first 19 × w bits (where w is the word width used) of RadioGatún's output is a cryptographically secure hash function. In other words, they claimed that the first 608 bits of the 32-bit version and 1216 bits of the 64-bit version of RadioGatún can be used as a cryptographic hash value.

In light of the birthday attack, this means that for a given word width w, RadioGatún is designed to have no attack with complexity less than 2^9.5w. This corresponds to 2³⁰⁴ for the 32-bit version and 2⁶⁰⁸ for the 64-bit version.

Since publishing the paper, the designers revised their security claim, and now claim that RadioGatún has the security of a cryptographic sponge function with a capacity of 19w. This means that the 32-bit version of RadioGatún can be used to make a hash with 304 bits of security (both from collision attacks and from Preimage attacks), and the 64-bit version offers 608 bits of security.

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