Tiger (hash)
| General | |
|---|---|
| Designers | Ross Anderson and Eli Biham |
| First published | 1996 |
| Detail | |
| Digest sizes | 192, 128, 160 |
| Rounds | 24 |
In cryptography, Tiger is a cryptographic hash function designed by Ross Anderson and Eli Biham in 1995 for efficiency on 64-bit platforms. The size of a Tiger hash value is 192 bits. Truncated versions (known as Tiger/128 and Tiger/160) can be used for compatibility with protocols assuming a particular hash size. Unlike the SHA-2 family, no distinguishing initialization values are defined; they are simply prefixes of the full Tiger/192 hash value.
Tiger2 is a variant where the message is padded by first appending a byte with the hexadecimal value of 0x80 as in MD4, MD5 and , rather than with the hexadecimal value of 0x01 as in the case of Tiger. The two variants are otherwise identical.
Tiger is designed using the nearly universal Merkle-Damgård paradigm. The one-way compression function operates on 64-bit words, maintaining 3 words of state and processing 8 words of data. There are 24 rounds, using a combination of operation mixing with XOR and addition/subtraction, rotates, and S-box lookups, and a fairly intricate key scheduling algorithm for deriving 24 round keys from the 8 input words.
Although fast in software, Tiger's large S-boxes (4 S-boxes, each with 256 64-bit entries totals 8 KiB) make implementations in hardware or small microcontrollers difficult.
Tiger is frequently used in Merkle hash tree form, where it is referred to as TTH (Tiger Tree Hash). TTH is used by many clients on the Direct Connect and Gnutella file sharing networks.
Tiger was considered for inclusion in the OpenPGP standard, but was abandoned in favor of RIPEMD-160.
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