Sha 1
SHA-1 (Secure Hash Algorithm) is a cryptographic hash function that was first published in 1995 in Federal Information Processing Standards (FIPS) PUB 180-1 by the National Security Agency (NSA) as a fix to an unknown flaw found in SHA-0.
In February of 2005 an attack was announced that could find collisions in SHA-1 requiring fewer than 269 operations.
Tools
On most Unix systems the tool sha1sum can be used to compute the SHA-1 hash of a file or devices.