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HMACSHA256 Constructor (Byte[])

Updated: January 2012

Initializes a new instance of the HMACSHA256 class with the specified key data.

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

public HMACSHA256(
	byte[] key
)

Parameters

key
Type: System.Byte[]
The secret key for HMACSHA256 encryption. The key can be any length. However, the recommended size is 64 bytes. If the secret key is more than 64 bytes long, it will be hashed (using SHA-256) to derive a 64-byte key. If it is less than 64 bytes long, it will be padded to 64 bytes.

ExceptionCondition
ArgumentNullException

The key parameter is null.

HMACSHA256 is a type of keyed hash algorithm that is constructed from the SHA-256 hash function and used as a 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, and then applies the hash function a second time. The output hash is 256 bits in length.

For an example of how to use this constructor, see the HMACSHA256 class.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Date

History

Reason

January 2012

Corrected parameter description.

Customer feedback.

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