This documentation is archived and is not being maintained.

HMACSHA1 Constructor (Byte[])

Updated: January 2011

Initializes a new instance of the HMACSHA1 class with the specified key data.

Namespace:  System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)

public HMACSHA1(
	byte[] key
)

Parameters

key
Type: System.Byte[]

The secret key for HMACSHA1 encryption. The key can be any length, but if it is more than 64 bytes long it will be hashed (using SHA-1) to derive a 64-byte key. Therefore, the recommended size of the secret key is 64 bytes.

ExceptionCondition
ArgumentNullException

The key parameter is null.

HMACSHA1 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 will be 160 bits (20 bytes) in length.

NoteNote:

This constructor creates an unmanaged instance of the algorithm using the SHA1CryptoServiceProvider class.

For an example of how to use this constructor, see the HMACSHA1 class.

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.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

Date

History

Reason

January 2011

Added note about SHA1CryptoServiceProvider.

Customer feedback.

Show: