File verification using SHA-1 is accomplished by comparing the checksums created after running the algorithm on the two files you want to compare.
SHA-1 is the second iteration of this cryptographic hash function, replacing the previous SHA-0. An SHA-2 cryptographic hash function is also available and SHA-3 is being developed.
All Secure Hash Algorithms were developed by the US National Security Agency.
MD5 is another commonly used cryptographic hash function.