|SHA, Secure Hash Algorithm|
|Output:||160 bit message digest.|
DSA, Digital Signature Application.
(RFC 1320) Digital signature application, is where a large file must be "compressed" in a secure manner before being encrypted with a private (secret) key under a public-key cryptosystem.
(RFC 2841) The secret authentication key shared between the communicating parties SHOULD be a cryptographically strong random number, not a guessable string of any sort.
(RFC 1320) The message-digest algorithm takes as input a message of arbitrary length and produces as output a "fingerprint" or "message digest" of the input. It is conjectured that it is computationally infeasible to produce two messages having the same message digest, or to produce any message having a given prespecified target message digest.
[RFC 2841] IP Authentication using Keyed SHA1 with Interleaved Padding (IP-MAC).
[RFC 3174] US Secure Hash Algorithm 1 (SHA1).
[RFC 3874] A 224-bit One-way Hash Function: SHA-224.
[RFC 4231] Identifiers and Test Vectors for HMAC-SHA-224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512.
[FIPS 180-2] Secure Hash Standard.
[RFC 1852] IP Authentication using Keyed SHA.