Streebog is a family of two hash algorithms, Streebog-256 and Streebog-512, defined in the Russian national standard GOST R 34.11-2012 Information Technology - Cryptographic Information Security - Hash Function. It is also described in RFC 6986. It is the competitor of NIST SHA-3 standard.
VeraCrypt uses only Streebog-512 which has an output size of 512 bits.
