GOST (block cipher)

GOST 28147-89 (Magma)

Diagram of GOST
General
Designers	USSR, KGB, 8th Department
First published	1994-05-23 (declassified)
Successors	GOST hash function, Kuznyechik
Certification	GOST standard
Cipher detail
Key sizes	256 bits
Block sizes	64 bits
Structure	Feistel network
Rounds	32
Best public cryptanalysis
In 2011 several authors discovered more significant flaws in GOST, being able to attack the full 32-round GOST with arbitrary keys for the first time. It has even been called "a deeply flawed cipher" by Nicolas Courtois.[1]

The GOST block cipher (Magma), defined in the standard GOST 28147-89 (RFC 5830), is a Soviet and Russian government standard symmetric key block cipher with a block size of 64 bits. The original standard, published in 1989, did not give the cipher any name, but the most recent revision of the standard, GOST R 34.12-2015 (RFC 7801, RFC 8891), specifies that it may be referred to as Magma.^[2] The GOST hash function is based on this cipher. The new standard also specifies a new 128-bit block cipher called Kuznyechik.

Developed in the 1970s, the standard had been marked "Top Secret" and then downgraded to "Secret" in 1990. Shortly after the dissolution of the USSR, it was declassified and it was released to the public in 1994. GOST 28147 was a Soviet alternative to the United States standard algorithm, DES.^[3] Thus, the two are very similar in structure.