AesManaged Class

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

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.
Top

  NameDescription
Public propertyBlockSizeGets or sets the block size, in bits, of the cryptographic operation. (Inherited from SymmetricAlgorithm.)
Public propertyFeedbackSizeGets or sets the number of bits to use as feedback. (Overrides SymmetricAlgorithm.FeedbackSize.)
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.)
Public propertyModeGets or sets the mode for operation of the symmetric algorithm. (Overrides SymmetricAlgorithm.Mode.)
Public propertyPaddingGets or sets the padding mode used in the symmetric algorithm. (Overrides SymmetricAlgorithm.Padding.)
Top

  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()).)
Public methodDisposeReleases all resources used by the current instance of the SymmetricAlgorithm class. (Inherited from SymmetricAlgorithm.)
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (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 the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (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.)
Top

  NameDescription
Explicit interface implemetationPrivate methodIDisposable.DisposeInfrastructure. Releases the unmanaged resources used by the SymmetricAlgorithm and optionally releases the managed resources. (Inherited from SymmetricAlgorithm.)
Top

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 RijndaelManaged class but limits blocks to 128 bits and does not allow feedback modes.

NoteNote

If the Windows security policy setting for Federal Information Processing Standards (FIPS)-compliant algorithms is enabled, using this algorithm throws a CryptographicException.

The following example demonstrates how to encrypt and decrypt sample data using the AesManaged class.

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



Class AesExample

    Public Shared Sub Main()
        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.
                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_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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Was this page helpful?
(1500 characters remaining)
Thank you for your feedback
Show:
© 2015 Microsoft