# Hierocrypt

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Family of block ciphers

Hierocrypt-L1 General Designers Toshiba First published 2000 Related to Hierocrypt-3 Certification CRYPTREC (Candidate) Cipher detail Key sizes 128 bits Block sizes 64 bits Structure Nested SPN Rounds 6.5 Best public cryptanalysis 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](/source/Cryptography), **Hierocrypt-L1** and **Hierocrypt-3** are [block ciphers](/source/Block_cipher) created by [Toshiba](/source/Toshiba) in 2000. They were submitted to the [NESSIE](/source/NESSIE) project, but were not selected.[3] Both algorithms were among the cryptographic techniques recommended for Japanese government use by [CRYPTREC](/source/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](/source/Block_size_(cryptography)): 64 bits for Hierocrypt-L1, 128 bits for Hierocrypt-3. Hierocrypt-L1's [key size](/source/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 [substitution–permutation network](/source/Substitution%E2%80%93permutation_network) (SPN) structure. Each round consists of parallel applications of a transformation called the *XS-box*, followed by a linear [diffusion](/source/Diffusion_(cryptography)) operation. The final half-round replaces the diffusion with a simple [post-whitening](/source/Key_whitening). The XS-box, which is shared by the two algorithms, is itself an SPN, consisting of a subkey [XOR](/source/XOR), an [S-box](/source/Substitution_box) lookup, a [linear diffusion](/source/Linear_diffusion), another subkey XOR, and another S-box lookup. The diffusion operations use two [MDS matrices](/source/MDS_matrix), and there is a single 8×8-bit S-box. The [key schedule](/source/Key_schedule) uses the binary expansions of the square roots of some small integers as a source of "[nothing up my sleeve numbers](/source/Nothing_up_my_sleeve_number)".

No [analysis](/source/Cryptanalysis) 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](/source/Integral_cryptanalysis) to reduced-round Hierocrypt variants; attacks faster than exhaustive search have been found for 3.5 rounds of each cipher.

## References

1. **[^](#cite_ref-1)** [P. Barreto](/source/Paulo_S._L._M._Barreto); [V. Rijmen](/source/Vincent_Rijmen); J. Nakahara Jr.; [B. Preneel](/source/Bart_Preneel); Joos Vandewalle; Hae Yong Kim (April 2001). *Improved SQUARE attacks against reduced-round HIEROCRYPT*. 8th International Workshop on [Fast Software Encryption](/source/Fast_Software_Encryption) (FSE 2001). [Yokohama](/source/Yokohama), Japan: [Springer-Verlag](/source/Springer-Verlag). pp. 165–173. [doi](/source/Doi_(identifier)):[10.1007/3-540-45473-X_14](https://doi.org/10.1007%2F3-540-45473-X_14).

1. **[^](#cite_ref-2)** Abdelkhalek, Ahmed; AlTawy, Riham; Tolba, Mohamed; Youssef, Amr M. (2015). "Meet-in-the-Middle Attacks on Reduced-Round Hierocrypt-3". *Progress in Cryptology -- LATINCRYPT 2015*. Lecture Notes in Computer Science. Vol. 9230. [Springer International Publishing](/source/Springer_International_Publishing). pp. 187–203. [doi](/source/Doi_(identifier)):[10.1007/978-3-319-22174-8_11](https://doi.org/10.1007%2F978-3-319-22174-8_11). [ISBN](/source/ISBN_(identifier)) [978-3-319-22174-8](https://en.wikipedia.org/wiki/Special:BookSources/978-3-319-22174-8).

1. **[^](#cite_ref-3)** Sean Murphy; Juliette White, eds. (2001-09-23). ["Security evaluation of NESSIE first phase"](https://www.cosic.esat.kuleuven.be/nessie/deliverables/D13.pdf) (PDF). Retrieved 2018-08-12.

## External links

- [256bit Ciphers - HIEROCRYPT Reference implementation and derived code](https://embeddedsw.net/Cipher_Reference_Home.html#HIEROCRYPT3)

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Adapted from the Wikipedia article [Hierocrypt](https://en.wikipedia.org/wiki/Hierocrypt) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Hierocrypt?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.