CIPHERUNICORN-A

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CIPHERUNICORN-A
General
Designers	NEC
First published	2000
Derived from	CIPHERUNICORN-E
Certification	CRYPTREC (Candidate)
Cipher detail
Key sizes	128, 192, or 256 bits
Block sizes	128 bits
Structure	nested Feistel network
Rounds	16

In cryptography, CIPHERUNICORN-A is a block cipher created by NEC in 2000. It was among the cryptographic techniques recommended for Japanese government use by CRYPTREC in 2003, however, has been dropped to "candidate" by CRYPTREC revision in 2013.

The algorithm uses a 16-round Feistel network structure similar to its predecessor, CIPHERUNICORN-E, but with significant changes. The block size is 128 bits, with key sizes of 128, 192, or 256 bits. The round function is even more complicated than that of CIPHERUNICORN-E, but the extra mixing function between rounds has been removed. The round function is still split into two nearly parallel computations; both of these are Feistel networks themselves. The first part (the main stream) is a 10-round Feistel network, using 4 8×8-bit S-boxes much like the ones from CIPHERUNICORN-E. The last two rounds of the main stream are influenced by the output of the second part (the temporary key generation function). This second, 6-round Feistel network uses modular multiplication, as well as 2 of the S-boxes. In contrast to CIPHERUNICORN-E, subkeys are added in only at the beginning of each main round.

The key schedule of CIPHERUNICORN-A makes repeated use of a function called MT, using modular multiplication and all of the S-boxes. A flaw was discovered in the key schedule, such that certain keys are equivalent, but it is unknown just how much of a weakness this is.

The great complexity of CIPHERUNICORN-A's round function has made it difficult to analyze. Some limited analysis has been done on simplified variants, showing that they are likely resistant to both differential and linear cryptanalysis.

References

Matt Robshaw (14 December 2001). A Cryptographic Review of CIPHERUNICORN-A (PDF). Retrieved 21 January 2007.

External links

256bit Ciphers - CIPHERUNICORN Reference implementation and derived code

v t e Block ciphers (security summary)

Common algorithms	AES Blowfish DES Triple DES Serpent Twofish

Less common algorithms	Camellia CAST-128 IDEA RC2 RC5 SEED Skipjack TEA XTEA

Other algorithms	3-Way Akelarre Anubis ARIA BaseKing BassOmatic BATON BEAR and LION CAST-256 Chiasmus CIKS-1 CIPHERUNICORN-A CIPHERUNICORN-E CLEFIA CMEA Cobra COCONUT98 Crab Cryptomeria/C2 CRYPTON CS-Cipher DEAL DES-X DFC E2 FEAL FEA-M FROG G-DES GOST Grand Cru Hasty Pudding cipher Hierocrypt ICE IDEA NXT Intel Cascade Cipher Iraqi KASUMI KeeLoq KHAZAD Khufu and Khafre KN-Cipher Ladder-DES Libelle LOKI97 LOKI89/91 Lucifer M6 M8 MacGuffin Madryga MAGENTA MARS Mercy MESH MISTY1 MMB MULTI2 MultiSwap New Data Seal NewDES Nimbus NOEKEON NUSH PRESENT Q RC6 REDOC Red Pike S-1 SAFER SAVILLE SC2000 SHACAL SHARK Simon SMS4 Speck Spectr-H64 Square SXAL/MBAL Threefish Treyfer UES Xenon xmx XXTEA Zodiac

Design	Feistel network Key schedule Lai-Massey scheme Product cipher S-box P-box SPN Avalanche effect Block size Key size Key whitening No weak keys

Attack (cryptanalysis)	Brute-force (EFF DES cracker) MITM Linear (Piling-up lemma) Differential (Impossible Truncated Higher-order) Differential-linear Integral (aka Square) Boomerang Mod n Related-key Slide Rotational Timing XSL Interpolation Partitioning Davies' Rebound

Standardization	AES process CRYPTREC NESSIE

Utilization	Initialization vector Mode of operation Padding

v t e Cryptography

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Symmetric-key algorithm Block cipher Stream cipher Public-key cryptography Cryptographic hash function Message authentication code Random numbers Steganography

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