GOST (ГОСТ) stands for Gosudarstvennyi Standard, which translates to "Government Standard" in Russian. The GOST block cipher is a symmetric key block cipher that was developed by the Soviet Union and later adopted as a national standard in Russia and other countries of the former Soviet Union.

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. 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. Thus, the two are very similar in structure.

Key Features

• Block Size: GOST operates on 64-bit blocks of data.
• Key Size: The key size is 256 bits, which provides a high level of security.
• Structure: GOST is a Feistel network with 32 rounds. Each round involves a substitution-permutation network (SPN) operation.
• S-boxes: GOST uses eight 4x4 S-boxes (substitution boxes) for non-linear transformations. These S-boxes can be chosen from a set of predefined tables or customized.
• Key Schedule: The key schedule generates 32 subkeys from the original 256-bit key. Each subkey is used in one of the 32 rounds of the cipher.

Main Functions

• Encrypt

• Decrypt

• Sign: Sign a plaintext message using one of the GOST block ciphers.

• Verify: Verify the signature of a plaintext message using one of the GOST block ciphers. Enter the signature in the MAC field.
• Key Wrap: A key wrapping algorithm for protecting keys in untrusted storage using one of the GOST block cipers.
• Key Unwrap: A decryptor for keys wrapped using one of the GOST block ciphers.

References

https://wikipedia.org/wiki/GOST_(block_cipher)