DES Class
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DES Class

Represents the base class for the Data Encryption Standard (DES) algorithm from which all DES implementations must derive.

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

'Declaration
<ComVisibleAttribute(True)> _
Public MustInherit Class DES _
	Inherits SymmetricAlgorithm

The DES type exposes the following members.

  NameDescription
Protected methodDESInitializes a new instance of the DES class.
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  NameDescription
Public propertyBlockSizeGets or sets the block size, in bits, of the cryptographic operation. (Inherited from SymmetricAlgorithm.)
Public propertyFeedbackSizeGets or sets the feedback size, in bits, of the cryptographic operation. (Inherited from SymmetricAlgorithm.)
Public propertyIVGets or sets the initialization vector (IV) for the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Public propertyKeyGets or sets the secret key for the Data Encryption Standard (DES) algorithm. (Overrides SymmetricAlgorithm.Key.)
Public propertyKeySizeGets or sets the size, in bits, of the secret key used by the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Public propertyLegalBlockSizesGets the block sizes, in bits, that are supported by the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Public propertyLegalKeySizesGets the key sizes, in bits, that are supported by the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Public propertyModeGets or sets the mode for operation of the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Public propertyPaddingGets or sets the padding mode used in the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
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  NameDescription
Public methodClearReleases all resources used by the SymmetricAlgorithm class. (Inherited from SymmetricAlgorithm.)
Public methodStatic memberCreateCreates an instance of a cryptographic object to perform the Data Encryption Standard (DES) algorithm.
Public methodStatic memberCreate(String)Creates an instance of a cryptographic object to perform the specified implementation of the Data Encryption Standard (DES) algorithm.
Public methodCreateDecryptorCreates a symmetric decryptor object with the current Key property and initialization vector (IV). (Inherited from SymmetricAlgorithm.)
Public methodCreateDecryptor(Byte(), Byte())When overridden in a derived class, creates a symmetric decryptor object with the specified Key property and initialization vector (IV). (Inherited from SymmetricAlgorithm.)
Public methodCreateEncryptorCreates a symmetric encryptor object with the current Key property and initialization vector (IV). (Inherited from SymmetricAlgorithm.)
Public methodCreateEncryptor(Byte(), Byte())When overridden in a derived class, creates a symmetric encryptor object with the specified Key property and initialization vector (IV). (Inherited from SymmetricAlgorithm.)
Public methodDisposeReleases all resources used by the current instance of the SymmetricAlgorithm class. (Inherited from SymmetricAlgorithm.)
Protected methodDispose(Boolean)Releases the unmanaged resources used by the SymmetricAlgorithm and optionally releases the managed resources. (Inherited from SymmetricAlgorithm.)
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 methodGenerateIVWhen overridden in a derived class, generates a random initialization vector (IV) to use for the algorithm. (Inherited from SymmetricAlgorithm.)
Public methodGenerateKeyWhen overridden in a derived class, generates a random key (Key) to use for the algorithm. (Inherited from SymmetricAlgorithm.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodStatic memberIsSemiWeakKeyDetermines whether the specified key is semi-weak.
Public methodStatic memberIsWeakKeyDetermines whether the specified key is weak.
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 methodValidKeySizeDetermines whether the specified key size is valid for the current algorithm. (Inherited from SymmetricAlgorithm.)
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  NameDescription
Protected fieldBlockSizeValueRepresents the block size, in bits, of the cryptographic operation. (Inherited from SymmetricAlgorithm.)
Protected fieldFeedbackSizeValueRepresents the feedback size, in bits, of the cryptographic operation. (Inherited from SymmetricAlgorithm.)
Protected fieldIVValueRepresents the initialization vector (IV) for the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Protected fieldKeySizeValueRepresents the size, in bits, of the secret key used by the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Protected fieldKeyValueRepresents the secret key for the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Protected fieldLegalBlockSizesValueSpecifies the block sizes, in bits, that are supported by the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Protected fieldLegalKeySizesValueSpecifies the key sizes, in bits, that are supported by the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Protected fieldModeValueRepresents the cipher mode used in the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
Protected fieldPaddingValueRepresents the padding mode used in the symmetric algorithm. (Inherited from SymmetricAlgorithm.)
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This algorithm supports a key length of 64 bits.

The following code example method uses DESCryptoServiceProvider (an implementation of DES) to encrypt a string to an in-memory buffer. It then decrypts and displays the round-tripped string.


Imports System
Imports System.IO
Imports System.Security.Cryptography



Class TripleDESCryptoServiceProviderExample

    Public Shared Sub Main()
        Try

            Dim original As String = "Here is some data to encrypt!"

            ' Create a new instance of the TripleDESCryptoServiceProvider
            ' class.  This generates a new key and initialization 
            ' vector (IV).
            Using myTripleDESCryptoServiceProvider As New TripleDESCryptoServiceProvider()

                ' Encrypt the string to an array of bytes.
                Dim encrypted As Byte() = EncryptStringToBytes(original, myTripleDESCryptoServiceProvider.Key, myTripleDESCryptoServiceProvider.IV)

                ' Decrypt the bytes to a string.
                Dim roundtrip As String = DecryptStringFromBytes(encrypted, myTripleDESCryptoServiceProvider.Key, myTripleDESCryptoServiceProvider.IV)

                'Display the original data and the decrypted data.
                Console.WriteLine("Original:   {0}", original)
                Console.WriteLine("Round Trip: {0}", roundtrip)
            End Using
        Catch e As Exception
            Console.WriteLine("Error: {0}", e.Message)
        End Try

    End Sub 'Main

    Shared Function EncryptStringToBytes(ByVal plainText As String, ByVal Key() As Byte, ByVal IV() As Byte) As Byte()
        ' Check arguments.
        If plainText Is Nothing OrElse plainText.Length <= 0 Then
            Throw New ArgumentNullException("plainText")
        End If
        If Key Is Nothing OrElse Key.Length <= 0 Then
            Throw New ArgumentNullException("Key")
        End If
        If IV Is Nothing OrElse IV.Length <= 0 Then
            Throw New ArgumentNullException("Key")
        End If
        Dim encrypted() As Byte
        ' Create an TripleDESCryptoServiceProvider object
        ' with the specified key and IV.
        Using tdsAlg As New TripleDESCryptoServiceProvider()

            tdsAlg.Key = Key
            tdsAlg.IV = IV

            ' Create a decrytor to perform the stream transform.
            Dim encryptor As ICryptoTransform = tdsAlg.CreateEncryptor(tdsAlg.Key, tdsAlg.IV)
            ' Create the streams used for encryption.
            Using msEncrypt As New MemoryStream()
                Using csEncrypt As New CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write)
                    Using swEncrypt As New StreamWriter(csEncrypt)

                        'Write all data to the stream.
                        swEncrypt.Write(plainText)
                    End Using
                    encrypted = msEncrypt.ToArray()
                End Using
            End Using
        End Using

        ' Return the encrypted bytes from the memory stream.
        Return encrypted

    End Function 'EncryptStringToBytes

    Shared Function DecryptStringFromBytes(ByVal cipherText() As Byte, ByVal Key() As Byte, ByVal IV() As Byte) As String
        ' Check arguments.
        If cipherText Is Nothing OrElse cipherText.Length <= 0 Then
            Throw New ArgumentNullException("cipherText")
        End If
        If Key Is Nothing OrElse Key.Length <= 0 Then
            Throw New ArgumentNullException("Key")
        End If
        If IV Is Nothing OrElse IV.Length <= 0 Then
            Throw New ArgumentNullException("Key")
        End If
        ' Declare the string used to hold
        ' the decrypted text.
        Dim plaintext As String = Nothing

        ' Create an TripleDESCryptoServiceProvider object
        ' with the specified key and IV.
        Using tdsAlg As New TripleDESCryptoServiceProvider
            tdsAlg.Key = Key
            tdsAlg.IV = IV

            ' Create a decrytor to perform the stream transform.
            Dim decryptor As ICryptoTransform = tdsAlg.CreateDecryptor(tdsAlg.Key, tdsAlg.IV)

            ' Create the streams used for decryption.
            Using msDecrypt As New MemoryStream(cipherText)

                Using csDecrypt As New CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read)

                    Using srDecrypt As New StreamReader(csDecrypt)


                        ' Read the decrypted bytes from the decrypting stream
                        ' and place them in a string.
                        plaintext = srDecrypt.ReadToEnd()
                    End Using
                End Using
            End Using
        End Using

        Return plaintext

    End Function 'DecryptStringFromBytes 
End Class


Decryption can be handled in the same way; use CreateDecryptor instead of CreateEncryptor. The same key (Key) and initialization vector (IV) used to encrypt the file must be used to decrypt it.

.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.

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