SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function designed by the National Security
Agency (NSA). It is used to generate a unique digital fingerprint of a file or message. The output
of SHA-1 is a fixed-length 160-bit hash, typically represented as a 40-digit hexadecimal number.
SHA-1 is a one-way function, meaning that it cannot be reversed to obtain the original input.
It is also designed to be collision-resistant, meaning that it is computationally infeasible to
find two inputs that hash to the same output.
Despite its historical importance, SHA-1 is no longer considered a secure hash function due to
vulnerabilities that have been discovered in its design. It has been officially deprecated by
NIST (National Institute of Standards and Technology) and replaced by the more secure SHA-2
and SHA-3 families of hash functions.