Secure Hash Algorithm 1 or SHA-1 is a cryptographic hash function designed by the United States National Security Agency and released in 1995. The algorithm was widely adopted in the industry for digital signatures and data integrity purposes. For example, applications would use SHA-1 to convert plain-text passwords into a hash that would be useless to a hacker, unless of course, the hacker could reverse engineer the hash back into the original password, which they could not. As for data integrity, an SHA-1 hash ensured that no two files would have the same hash, and even the slightest change in a file would result in a new, completely unique hash.
SHA-1 Has Been Compromised In Practice
February 24, 2017 for Auth0