Updated: May 2011
Computes a Hash-based Message Authentication Code (HMAC) using the SHA1 hash function.
Assembly: mscorlib (in mscorlib.dll)
is a type of keyed hash algorithm that is constructed from the SHA-1 hash function and used as an HMAC, or hash-based message authentication code. The HMAC process mixes a secret key with the message data, hashes the result with the hash function, mixes that hash value with the secret key again, then applies the hash function a second time. The output hash is 160 bits in length.
An HMAC can be used to determine whether a message sent over an insecure channel has been tampered with, provided that the sender and receiver share a secret key. The sender computes the hash value for the original data and sends both the original data and hash value as a single message. The receiver recalculates the hash value on the received message and checks that the computed HMAC matches the transmitted HMAC.
Any change to the data or the hash value will result in a mismatch, because knowledge of the secret key is required to change the message and reproduce the correct hash value. Therefore, if the original and computed hash values match, the message is authenticated.
The SHA-1 (Secure Hash Algorithm, also called SHS, Secure Hash Standard) is a cryptographic hash algorithm published by the United States Government. It produces a 160-bit hash value from an arbitrary length string.
accepts keys of any size, and produces a hash sequence of length 160 bits.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.