SHA-1 (160 bit) is a cryptographic hash function designed by the United States National Security Agency and published by the United States NIST as a U.S. Federal Information Processing Standard.

SHA-1 produces a 160-bit (20-byte) hash value. A SHA-1 hash value is typically expressed as a hexadecimal number, 40 digits long.

SHA-1 is the most widely used of the existing SHA hash functions, and is employed in several widely used applications and protocols.