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SymmetricAlgorithm Class

Represents the abstract base class from which all implementations of symmetric algorithms must inherit.

System.Object
  System.Security.Cryptography.SymmetricAlgorithm
    System.Security.Cryptography.Aes

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

[ComVisibleAttribute(true)]
public abstract class SymmetricAlgorithm : IDisposable

The SymmetricAlgorithm type exposes the following members.

  NameDescription
Protected methodSupported by Silverlight for Windows PhoneSymmetricAlgorithmInitializes a new instance of the SymmetricAlgorithm class.
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  NameDescription
Public propertySupported by Silverlight for Windows PhoneBlockSizeGets or sets the block size, in bits, of the cryptographic operation.
Public propertySupported by Silverlight for Windows PhoneIVGets or sets the initialization vector (IV) for the symmetric algorithm.
Public propertySupported by Silverlight for Windows PhoneKeyGets or sets the secret key for the symmetric algorithm.
Public propertySupported by Silverlight for Windows PhoneKeySizeGets or sets the size, in bits, of the secret key used by the symmetric algorithm.
Public propertySupported by Silverlight for Windows PhoneLegalBlockSizesGets the block sizes, in bits, that are supported by the symmetric algorithm.
Public propertySupported by Silverlight for Windows PhoneLegalKeySizesGets the key sizes, in bits, that are supported by the symmetric algorithm.
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  NameDescription
Public methodSupported by Silverlight for Windows PhoneClearReleases all resources used by the SymmetricAlgorithm class.
Public methodSupported by Silverlight for Windows PhoneCreateDecryptor()Creates a symmetric decryptor object with the current Key property and initialization vector (IV).
Public methodSupported by Silverlight for Windows PhoneCreateDecryptor(Byte[], Byte[])When overridden in a derived class, creates a symmetric decryptor object with the specified Key property and initialization vector (IV).
Public methodSupported by Silverlight for Windows PhoneCreateEncryptor()Creates a symmetric encryptor object with the current Key property and initialization vector (IV).
Public methodSupported by Silverlight for Windows PhoneCreateEncryptor(Byte[], Byte[])When overridden in a derived class, creates a symmetric encryptor object with the specified Key property and initialization vector (IV).
Protected methodSupported by Silverlight for Windows PhoneDisposeReleases the unmanaged resources used by the SymmetricAlgorithm and optionally releases the managed resources.
Public methodSupported by Silverlight for Windows PhoneEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows PhoneFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneGenerateIVWhen overridden in a derived class, generates a random initialization vector (IV) to use for the algorithm.
Public methodSupported by Silverlight for Windows PhoneGenerateKeyWhen overridden in a derived class, generates a random key (Key) to use for the algorithm.
Public methodSupported by Silverlight for Windows PhoneGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows PhoneMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneToStringReturns a string that represents the current object. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneValidKeySizeDetermines whether the specified key size is valid for the current algorithm.
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  NameDescription
Protected fieldSupported by Silverlight for Windows PhoneBlockSizeValueRepresents the block size, in bits, of the cryptographic operation.
Protected fieldSupported by Silverlight for Windows PhoneIVValueRepresents the initialization vector (IV) for the symmetric algorithm.
Protected fieldSupported by Silverlight for Windows PhoneKeySizeValueRepresents the size, in bits, of the secret key used by the symmetric algorithm.
Protected fieldSupported by Silverlight for Windows PhoneKeyValueRepresents the secret key for the symmetric algorithm.
Protected fieldSupported by Silverlight for Windows PhoneLegalBlockSizesValueSpecifies the block sizes, in bits, that are supported by the symmetric algorithm.
Protected fieldSupported by Silverlight for Windows PhoneLegalKeySizesValueSpecifies the key sizes, in bits, that are supported by the symmetric algorithm.
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  NameDescription
Explicit interface implemetationPrivate methodSupported by Silverlight for Windows PhoneIDisposable.DisposeInfrastructure. Releases the unmanaged resources used by the SymmetricAlgorithm and optionally releases the managed resources.
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The classes that derive from the SymmetricAlgorithm class use a chaining mode called cipher block chaining (CBC), which requires a key (Key) and an initialization vector (IV) to perform cryptographic transformations on data. To decrypt data that was encrypted using one of the SymmetricAlgorithm classes, you must set the Key property and the IV property to the same values that were used for encryption. For a symmetric algorithm to be useful, the secret key must be known only to the sender and the receiver.

AesManaged is an implementation of the SymmetricAlgorithm class.

Note that when using derived classes, it is not enough, from a security perspective, to simply force a garbage collection after you have finished using the object. You must explicitly call the Clear method on the object to zero out any sensitive data within the object before it is released. Note that garbage collection does not zero out the contents of collected objects but simply marks the memory as available for reallocation. Thus the data contained within a garbage collected object may still be present in the memory heap in unallocated memory. In the case of cryptographic objects, this data could contain sensitive information such as key data or a block of plain text.

All cryptographic classes in the .NET Framework that hold sensitive data implement a Clear method. When called, the Clear method overwrites all sensitive data within the object with zeros and then releases the object so that it can be safely garbage collected. When the object has been zeroed and released, you should then call the Dispose method with the disposing parameter set to True to dispose of all managed and unmanaged resources associated with the object.

Notes to Inheritors

When you inherit from the SymmetricAlgorithm class, you must override the following members: CreateDecryptor, CreateEncryptor, GenerateIV, and GenerateKey.

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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

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