CryptoSys Home > API > SHA-1 cryptography software

SHA-1 cryptography software

The Secure Hash Algorithm (SHA-1) produces a condensed representation of a message or a data file that can be used by both the transmitter and intended receiver of the message and to verify a digital signature.

SHA-1 is specified in FIPS PUB 180 Secure Hash Standard, (pdf-link).

SHA-1 can process a message of up to 2⁶⁴ bits (that's 2⁵⁶ bytes or 64 Petabytes - a lot!) and produces a message digest of 160 bits (20 bytes). The SHA-1 is called secure because it is computationally infeasible to find a message which corresponds to a given message digest, or to find two different messages which produce the same message digest. Any change to a message in transit will, with very high probability, result in a different message digest, and the signature will fail to verify. SHA-1 is preferred over the less-secure MD5 message digest algorithm.

The SHA-1 function is no longer considered as secure as it was designed to be. Read RFC4270 Attacks on Cryptographic Hashes in Internet Protocols. For better security, consider using the 256-bit SHA-256 secure hash algorithm.

SHA-1 functions available in CryptoSys API

VB6/C Functions	.NET methods
`SHA1_StringHexHash` `SHA1_BytesHexHash` `SHA1_FileHexHash` `SHA1_Init` `SHA1_AddBytes` `SHA1_AddString` `SHA1_HexDigest` `SHA1_Reset` `SHA1_Hmac`	`Sha1.HexHash Method (String)` `Sha1.HexHash Method (Byte[])` `Sha1.FileHexHash Method` `Sha1.Init Method` `Sha1.AddData Method (Byte[])` `Sha1.AddData Method (String)` `Sha1.HexDigest Method` `Sha1.Reset Method` `Sha1.Hmac Method`

The SHA_1Hmac function provides HMAC, a mechanism for message authentication using the SHA-1 cryptographic hash function. For more details, refer to RFC 2104 HMAC: Keyed-Hashing for Message Authentication, Krawczyk, Bellare and Canetti, February 1997 or FIPS PUB 198 The Keyed-Hash Message Authentication Code (HMAC), March 2002, (pdf 173 kB).

Contact us

For more information or to comment on this page, please send us a message.

This page last updated 15 August 2025.