Mugi

Mugi may refer to:

MUGI

In cryptography, MUGI is a pseudorandom number generator (PRNG) designed for use as a stream cipher. 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.

MUGI takes a 128-bit secret key and a 128-bit initial vector (IV). After a key- and IV- setup process, MUGI outputs 64-bit output strings based on the internal state, while updating the internal state after each output block. MUGI has a 1216-bit internal state; there are three 64-bit registers (the "state") and 16 64-bit registers (the "buffer").

MUGI uses the non-linear S-box that was originally defined in Advanced Encryption Standard (AES). A part of the linear transformation also reuses the MDS matrix of AES. The basic design is influenced by that of Panama.

Security

As of September 2006, there are no known attacks against MUGI that are faster than serial brute-force of the key space or of the internal state.

In the paper, "A weakness of the linear part of stream cipher MUGI", by Golic Jovan Dj, Roy Bimal and Meier Willi, the abstract claims: "The linearly updated component of the stream cipher MUGI, called the buffer, is analyzed theoretically by using the generating function method. In particular, it is proven that the intrinsic response of the buffer, without the feedback from the nonlinearly updated component, consists of binary linear recurring sequences with small linear complexity 32 and with extremely small period 48. It is then shown how this weakness can in principle be used to facilitate the linear cryptanalysis of MUGI with two main objectives: to reconstruct the secret key and to find linear statistical distinguishers."