Unkeyed cryptographic

Tiger

Designed by Ross Anderson and Eli Biham in 1995. Tiger was one of the first hash functions explicitly designed for 64-bit processors, well ahead of its time. 192-bit output, S-box-based round function, designed to be three times faster than SHA-1 on Alpha hardware.

At a glance

Where it shows up

• Tiger Tree Hash (TTH) , binary tree of Tiger hashes used in ed2k, eDonkey, DC++, Gnutella2 to identify and verify chunks of large files.
• Direct Connect P2P clients , TTH for file IDs.
• Some early Linux fingerprint tools.

Tiger2

A 2005 update changed the padding from the original Tiger’s 0x01 first padding byte to 0x80 , aligning with most other hash functions. Tiger2 produces different digests from Tiger for the same input. Most TTH implementations use the original Tiger.

Security status

Best published attacks cover reduced-round variants (Mendel, Rijmen): pseudo-near-collisions on 16 of 24 rounds. Full Tiger has no practical break. The reason Tiger doesn’t see modern use is its 192-bit output (only 96-bit collision security) and the dominance of SHA-2 / SHA-3 in standard-track contexts.

References

• Anderson & Biham , Tiger: A Fast New Hash Function (1995)
• Wikipedia , Tiger (hash function)
• SHA-256