Hierocrypt

Hierocrypt-L1

General
Designers	Integral attack against 3.5 rounds[1]

Hierocrypt-3

General
Designers	Toshiba
First published	2000
Related to	Hierocrypt-L1
Certification	CRYPTREC (Candidate)
Cipher detail
Key sizes	128, 192, or 256 bits
Block sizes	128 bits
Structure	Nested SPN
Rounds	6.5, 7.5, or 8.5
Best public cryptanalysis
Meet-in-the-middle attack against 4 rounds[2]

In cryptography, Hierocrypt-L1 and Hierocrypt-3 are block ciphers created by Toshiba in 2000. They were submitted to the NESSIE project, but were not selected.^[3] Both algorithms were among the cryptographic techniques recommended for Japanese government use by CRYPTREC in 2003, however, both have been dropped to "candidate" by CRYPTREC revision in 2013.

The Hierocrypt ciphers are very similar, differing mainly in block size: 64 bits for Hierocrypt-L1, 128 bits for Hierocrypt-3. Hierocrypt-L1's key size is 128 bits, while Hierocrypt-3 can use keys of 128, 192, or 256 bits. The number of rounds of encryption also varies: Hierocrypt-L1 uses 6.5 rounds, and Hierocrypt-3 uses 6.5, 7.5, or 8.5, depending on the key size.

The Hierocrypt ciphers use a nested

operation. The final half-round replaces the diffusion with a simple ".

No analysis of the full ciphers has been announced, but certain weaknesses were discovered in the Hierocrypt key schedule, linear relationships between the master key and some subkeys. There has also been some success applying integral cryptanalysis to reduced-round Hierocrypt variants; attacks faster than exhaustive search have been found for 3.5 rounds of each cipher.

References

External links

• 256bit Ciphers - HIEROCRYPT Reference implementation and derived code