AesCryptoServiceProvider.CreateDecryptor Method

Definition

Namespace:

System.Security.Cryptography

Assembly:

System.Security.Cryptography.dll

Creates a symmetric AES decryptor object.

Overloads

CreateDecryptor()	Creates a symmetric AES decryptor object using the current key and initialization vector (IV).
CreateDecryptor(Byte[], Byte[])	Creates a symmetric AES decryptor object using the specified key and initialization vector (IV).

CreateDecryptor()

Source:

AesCryptoServiceProvider.cs

Creates a symmetric AES decryptor object using the current key and initialization vector (IV).

public:
 override System::Security::Cryptography::ICryptoTransform ^ CreateDecryptor();

public override System.Security.Cryptography.ICryptoTransform CreateDecryptor ();

override this.CreateDecryptor : unit -> System.Security.Cryptography.ICryptoTransform

Public Overrides Function CreateDecryptor () As ICryptoTransform

Returns

ICryptoTransform

A symmetric AES decryptor object.

Exceptions

CryptographicException

The current key is invalid or missing.

CreateDecryptor(Byte[], Byte[])

Source:

AesCryptoServiceProvider.cs

Creates a symmetric AES decryptor object using the specified key and initialization vector (IV).

public:
 override System::Security::Cryptography::ICryptoTransform ^ CreateDecryptor(cli::array <System::Byte> ^ rgbKey, cli::array <System::Byte> ^ rgbIV);

public override System.Security.Cryptography.ICryptoTransform CreateDecryptor (byte[] rgbKey, byte[]? rgbIV);

override this.CreateDecryptor : byte[] * byte[] -> System.Security.Cryptography.ICryptoTransform

Public Overrides Function CreateDecryptor (rgbKey As Byte(), rgbIV As Byte()) As ICryptoTransform

Parameters

rgbKey

Byte[]

The secret key to use for the symmetric algorithm.

rgbIV

Byte[]

The initialization vector to use for the symmetric algorithm.

Returns

ICryptoTransform

A symmetric AES decryptor object.

Exceptions

ArgumentNullException

key or iv is null.

ArgumentException

key is invalid.

Examples

The following example shows how to use the AesCryptoServiceProvider.CreateDecryptor method to decrypt an encrypted message. This code example is part of a larger example provided for the AesCryptoServiceProvider class.

static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] Key, byte[] IV)
{
    // Check arguments.
    if (cipherText == null || cipherText.Length <= 0)
        throw new ArgumentNullException("cipherText");
    if (Key == null || Key.Length <= 0)
        throw new ArgumentNullException("Key");
    if (IV == null || IV.Length <= 0)
        throw new ArgumentNullException("IV");

    // Declare the string used to hold
    // the decrypted text.
    string plaintext = null;

    // Create an AesCryptoServiceProvider object
    // with the specified key and IV.
    using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
    {
        aesAlg.Key = Key;
        aesAlg.IV = IV;

        // Create a decryptor to perform the stream transform.
        ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

        // Create the streams used for decryption.
        using (MemoryStream msDecrypt = new MemoryStream(cipherText))
        {
            using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
            {
                using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                {

                    // Read the decrypted bytes from the decrypting stream
                    // and place them in a string.
                    plaintext = srDecrypt.ReadToEnd();
                }
            }
        }
    }

    return plaintext;
}

    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("IV")
        End If
        ' Declare the string used to hold
        ' the decrypted text.
        Dim plaintext As String = Nothing

        ' Create an AesCryptoServiceProvider object
        ' with the specified key and IV.
        Using aesAlg As New AesCryptoServiceProvider()

            aesAlg.Key = Key
            aesAlg.IV = IV

            ' Create a decryptor 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

let decryptStringFromBytes_Aes (cipherText : byte[], key : byte[], iv : byte[]) : string =

    // Check arguments.
    if (isNull cipherText || cipherText.Length <= 0) then nullArg "cipherText"
    if (isNull key || key.Length <= 0) then nullArg "key"
    if (isNull iv || iv.Length <= 0) then nullArg "iv"

    // Create an AesCryptoServiceProvider object
    // with the specified key and IV.
    use aesAlg = new AesCryptoServiceProvider()
    aesAlg.Key <- key
    aesAlg.IV <- iv

    // Create a decryptor to perform the stream transform.
    let decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV)

    // Create the streams used for decryption.
    use msDecrypt = new MemoryStream(cipherText)
    use csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read)
    use srDecrypt = new StreamReader(csDecrypt)

    // Read the decrypted bytes from the decrypting stream
    // and return the resulting string.
    srDecrypt.ReadToEnd()