SM4

SM4 , formerly SMS4, is a block encryption used in the Chinese WLAN security standard WAPI with a key length and block size of 128 bits. After initially classified as secret, the algorithm was released in 2006.

Procedure

The 128-bit key is expanded to 32 round keys with 32 bits each. The 128-bit input is divided into 4 32-bit words . The encryption takes place in 32 rounds, whereby the round function operates on only one 32-bit word in each round. In terms of structure, SMS4 is an unbalanced Feistel cipher with 32 rounds. The round function consists of a non-linear substitution based on an 8-bit S-box and a linear substitution.

safety

During the cryptanalysis of SMS4, researchers found security problems in the round function.

Individual evidence

↑ SMS4 Encryption Algorithm for Wireless Networks . 2010 ( iacr.org ).
↑ Muhammad Reza Z'aba, Leonie Simpson, Ed Dawson and Kenneth Wong: Linearity within the SMS4 block cipher . In: Information Security and Cryptology . 2011, p. 248-265 . : "These findings raise serious questions on the security provided by SMS4."

[1] SMS4 Encryption Algorithm for Wireless Networks . 2010 ( iacr.org ).

[2] Muhammad Reza Z'aba, Leonie Simpson, Ed Dawson and Kenneth Wong: Linearity within the SMS4 block cipher . In: Information Security and Cryptology . 2011, p. 248-265 . : "These findings raise serious questions on the security provided by SMS4."