AesManaged Class

AesManaged Class

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Provides a managed implementation of the Advanced Encryption Standard (AES) symmetric algorithm.

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

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

'Declaration
Public NotInheritable Class AesManaged _
	Inherits Aes

The AesManaged type exposes the following members.

  NameDescription
Public methodAesManagedInitializes a new instance of the AesManaged class.
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  NameDescription
Public propertyBlockSizeGets or sets the block size, in bits, of the cryptographic operation. (Inherited from SymmetricAlgorithm.)
Public propertyIVGets or sets the initialization vector (IV) to use for the symmetric algorithm. (Overrides SymmetricAlgorithm.IV.)
Public propertyKeyGets or sets the secret key used for the symmetric algorithm. (Overrides SymmetricAlgorithm.Key.)
Public propertyKeySizeGets or sets the size, in bits, of the secret key used for the symmetric algorithm. (Overrides SymmetricAlgorithm.KeySize.)
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.)
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  NameDescription
Public methodClearReleases all resources used by the SymmetricAlgorithm class. (Inherited from SymmetricAlgorithm.)
Public methodCreateDecryptorCreates a symmetric decryptor object using the current key and initialization vector (IV). (Overrides SymmetricAlgorithm.CreateDecryptor.)
Public methodCreateDecryptor(Byte(), Byte())Creates a symmetric decryptor object using the specified key and initialization vector (IV). (Overrides SymmetricAlgorithm.CreateDecryptor(Byte(), Byte()).)
Public methodCreateEncryptorCreates a symmetric encryptor object using the current key and initialization vector (IV). (Overrides SymmetricAlgorithm.CreateEncryptor.)
Public methodCreateEncryptor(Byte(), Byte())Creates a symmetric encryptor object using the specified key and initialization vector (IV). (Overrides SymmetricAlgorithm.CreateEncryptor(Byte(), Byte()).)
Protected methodDisposeReleases 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 the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGenerateIVGenerates a random initialization vector (IV) to use for the symmetric algorithm. (Overrides SymmetricAlgorithm.GenerateIV.)
Public methodGenerateKeyGenerates a random key to use for the symmetric algorithm. (Overrides SymmetricAlgorithm.GenerateKey.)
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 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 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.)
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  NameDescription
Explicit interface implemetationPrivate methodIDisposable.DisposeInfrastructure. Releases the unmanaged resources used by the SymmetricAlgorithm and optionally releases the managed resources. (Inherited from SymmetricAlgorithm.)
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The AES algorithm is essentially the Rijndael symmetric algorithm with a fixed block size and iteration count. This class functions the same way as the .NET Framework RijndaelManaged class but limits blocks to 128 bits and does not allow feedback modes.

The cipher mode is always CBC, and the padding mode is always PKCS7.

The following example demonstrates how to encrypt and decrypt an isolated storage file by using the AesManaged class. To build and run this example, create a Windows Phone app in Visual Studio named AesManaged and replace the MainPage.xaml file and the MainPage.xaml.cs (or MainPage.xaml.vb) file with the following code.

NoteNote:

If the XAML code is not displayed, click the Language Filter arrow at the top of this page, and select the XAML check box.


Imports System.IO
Imports System.Security.Cryptography



Class Example

    Public Shared Sub Demo(outputBlock As System.Windows.Controls.TextBlock)
        Try

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

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

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

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

                'Display the original data and the decrypted data.
                outputBlock.Text += String.Format("Original:   {0}", original) + Environment.NewLine
                outputBlock.Text += String.Format("Round Trip: {0}", roundtrip) + Environment.NewLine
            End Using
        Catch e As Exception
            outputBlock.Text += String.Format("Error: {0}", e.Message) + Environment.NewLine
        End Try

    End Sub 'Demo(outputBlock As System.Windows.Controls.TextBlock)

    Shared Function EncryptStringToBytes_Aes(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 AesManaged object
        ' with the specified key and IV.
        Using aesAlg As New AesManaged()

            aesAlg.Key = Key
            aesAlg.IV = IV

            ' Create a decrytor to perform the stream transform.
            Dim encryptor As ICryptoTransform = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.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_Aes

    Shared Function DecryptStringFromBytes_Aes(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 AesManaged object
        ' with the specified key and IV.
        Using aesAlg As New AesManaged
            aesAlg.Key = Key
            aesAlg.IV = IV

            ' Create a decrytor to perform the stream transform.
            Dim decryptor As ICryptoTransform = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.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_Aes 
End Class 'AesExample


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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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