In cryptography

Cryptography

Cryptography is the practice and study of techniques for secure communication in the presence of third parties...

, SC2000 is a block cipher

Block cipher

In cryptography, a block cipher is a symmetric key cipher operating on fixed-length groups of bits, called blocks, with an unvarying transformation. A block cipher encryption algorithm might take a 128-bit block of plaintext as input, and output a corresponding 128-bit block of ciphertext...

 invented by a research group at Fujitsu

Fujitsu

is a Japanese multinational information technology equipment and services company headquartered in Tokyo, Japan. It is the world's third-largest IT services provider measured by revenues....

 Labs. It was submitted to the NESSIE

NESSIE

NESSIE was a European research project funded from 2000–2003 to identify secure cryptographic primitives. The project was comparable to the NIST AES process and the Japanese Government-sponsored CRYPTREC project, but with notable differences from both...

 project, but was not selected. SC2000 is one of the cryptographic techniques recommended for Japanese government use by CRYPTREC

CRYPTREC

CRYPTREC is the Cryptography Research and Evaluation Committees set up by the Japanese Government to evaluate and recommend cryptographic techniques for government and industrial use...

.

The algorithm uses a key size of 128, 192, or 256 bits. It operates on blocks of 128 bits using 6.5 or 7.5 rounds of encryption. Each round consists of S-box

Substitution box

In cryptography, an S-Box is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext — Shannon's property of confusion...

 lookups, key additions, and an unkeyed two-round Feistel network

Feistel cipher

In cryptography, a Feistel cipher is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel who did pioneering research while working for IBM ; it is also commonly known as a Feistel network. A large proportion of block...

. There are 3 S-boxes: a 4×4-bit one used at the beginning of each round, and a 5×5-bit one and 6×6-bit one used in the Feistel network.

No analysis

Cryptanalysis

Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...

 of the full SC2000 has been announced, but a reduced-round variant of 4.5 rounds is susceptible to both differential

Differential cryptanalysis

Differential cryptanalysis is a general form of cryptanalysis applicable primarily to block ciphers, but also to stream ciphers and cryptographic hash functions. In the broadest sense, it is the study of how differences in an input can affect the resultant difference at the output...

 and linear cryptanalysis

Linear cryptanalysis

In cryptography, linear cryptanalysis is a general form of cryptanalysis based on finding affine approximations to the action of a cipher. Attacks have been developed for block ciphers and stream ciphers...

.

External links

• Reference implementation and derived code