SM4 cipher algorithms (OSCCA GB/T 32907-2016).

SM4 (GBT.32907-2016) is a cryptographic standard issued by the
Organization of State Commercial Administration of China (OSCCA)
as an authorized cryptographic algorithms for the use within China.

SMS4 was originally created for use in protecting wireless
networks, and is mandated in the Chinese National Standard for
Wireless LAN WAPI (Wired Authentication and Privacy Infrastructure)
(GB.15629.11-2003).

The latest SM4 standard (GBT.32907-2016) was proposed by OSCCA and
standardized through TC 260 of the Standardization Administration
of the People's Republic of China (SAC).

The input, output, and key of SMS4 are each 128 bits.

See also: <https://eprint.iacr.org/2008/329.pdf>

If unsure, say N.

source code:

crypto/sm4_generic.c