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MACTripleDES Class

Updated: May 2011

Computes a Message Authentication Code (MAC) using TripleDES for the input data CryptoStream.

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

[ComVisibleAttribute(true)]
public ref class MACTripleDES : public KeyedHashAlgorithm

The MACTripleDES type exposes the following members.

  NameDescription
Public methodMACTripleDES()Initializes a new instance of the MACTripleDES class.
Public methodMACTripleDES(array<Byte>)Initializes a new instance of the MACTripleDES class with the specified key data.
Public methodMACTripleDES(String, array<Byte>)Initializes a new instance of the MACTripleDES class with the specified key data using the specified implementation of TripleDES.
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  NameDescription
Public propertyCanReuseTransformGets a value indicating whether the current transform can be reused. (Inherited from HashAlgorithm.)
Public propertyCanTransformMultipleBlocksWhen overridden in a derived class, gets a value indicating whether multiple blocks can be transformed. (Inherited from HashAlgorithm.)
Public propertyHashGets the value of the computed hash code. (Inherited from HashAlgorithm.)
Public propertyHashSizeGets the size, in bits, of the computed hash code. (Inherited from HashAlgorithm.)
Public propertyInputBlockSizeWhen overridden in a derived class, gets the input block size. (Inherited from HashAlgorithm.)
Public propertyKeyGets or sets the key to use in the hash algorithm. (Inherited from KeyedHashAlgorithm.)
Public propertyOutputBlockSizeWhen overridden in a derived class, gets the output block size. (Inherited from HashAlgorithm.)
Public propertyPaddingGets or sets the padding mode used in the hashing algorithm.
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  NameDescription
Public methodClearReleases all resources used by the HashAlgorithm class. (Inherited from HashAlgorithm.)
Public methodComputeHash(array<Byte>)Computes the hash value for the specified byte array. (Inherited from HashAlgorithm.)
Public methodComputeHash(Stream)Computes the hash value for the specified Stream object. (Inherited from HashAlgorithm.)
Public methodComputeHash(array<Byte>, Int32, Int32)Computes the hash value for the specified region of the specified byte array. (Inherited from HashAlgorithm.)
Public methodDispose()Releases all resources used by the current instance of the HashAlgorithm class. (Inherited from HashAlgorithm.)
Protected methodDispose(Boolean)Releases the unmanaged resources used by the MACTripleDES and optionally releases the managed resources. (Overrides KeyedHashAlgorithm::Dispose(Boolean).)
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodHashCoreRoutes data written to the object into the TripleDES encryptor for computing the Message Authentication Code (MAC). (Overrides HashAlgorithm::HashCore(array<Byte>, Int32, Int32).)
Protected methodHashFinalReturns the computed Message Authentication Code (MAC) after all data is written to the object. (Overrides HashAlgorithm::HashFinal().)
Public methodInitializeInitializes an instance of MACTripleDES. (Overrides HashAlgorithm::Initialize().)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodTransformBlockComputes the hash value for the specified region of the input byte array and copies the specified region of the input byte array to the specified region of the output byte array. (Inherited from HashAlgorithm.)
Public methodTransformFinalBlockComputes the hash value for the specified region of the specified byte array. (Inherited from HashAlgorithm.)
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  NameDescription
Protected fieldHashSizeValueRepresents the size, in bits, of the computed hash code. (Inherited from HashAlgorithm.)
Protected fieldHashValueRepresents the value of the computed hash code. (Inherited from HashAlgorithm.)
Protected fieldKeyValueThe key to use in the hash algorithm. (Inherited from KeyedHashAlgorithm.)
Protected fieldStateRepresents the state of the hash computation. (Inherited from HashAlgorithm.)
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A MAC 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 MAC for the original data, and sends both as a single message. The receiver recomputes the MAC on the received message, and checks that the computed MAC matches the transmitted MAC.

Any change to the data or the MAC will result in a mismatch, because knowledge of the secret key is required to change the message and reproduce the correct MAC. Therefore, if the codes match, the message is authenticated.

MACTripleDES uses a key of length 16 or 24 bytes, and produces a hash sequence of length 8 bytes.

The following example creates a MAC for a file named input.txt, which is located in the folder that contains the sample executable. The MAC and the original text are written to a file named encrypted.hsh in the same folder. The signed file is then read, and the MAC is calculated for the text portion of the file and compared to the MAC contained with the text.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.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.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Date

History

Reason

May 2011

Replaced the example with a new example that round-trips a file and checks the text for tampering.

Information enhancement.

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