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AesCbc.cs
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AesCbc.cs
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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License. See License.txt in the project root for
// license information.
using System.Security.Cryptography;
namespace Microsoft.Azure.KeyVault.Cryptography.Algorithms
{
/// <summary>
/// Abstract base class for vanilla AESCBC
/// </summary>
public abstract class AesCbc : SymmetricEncryptionAlgorithm
{
private static Aes Create( byte[] key, byte[] iv )
{
var aes = Aes.Create();
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
aes.KeySize = key.Length * 8;
aes.Key = key;
aes.IV = iv;
return aes;
}
protected AesCbc( string name )
: base( name )
{
}
public override ICryptoTransform CreateDecryptor( byte[] key, byte[] iv, byte[] authenticationData, byte[] authenticationTag )
{
if ( key == null )
throw new CryptographicException( "No key material" );
if ( iv == null )
throw new CryptographicException( "No initialization vector" );
// Note that authenticationData and authenticationTag are ignored.
// Create the AES provider
using ( var aes = Create( key, iv ) )
{
return aes.CreateDecryptor();
}
}
public override ICryptoTransform CreateEncryptor( byte[] key, byte[] iv, byte[] authenticationData )
{
if ( key == null )
throw new CryptographicException( "No key material" );
if ( iv == null )
throw new CryptographicException( "No initialization vector" );
// Create the AES provider
using ( var aes = Create(key, iv ) )
{
return aes.CreateEncryptor();
}
}
}
/// <summary>
/// AESCBC 128bit key with PKCS7 Padding
/// </summary>
public class Aes128Cbc : AesCbc
{
public const string AlgorithmName = "A128CBC";
const int KeySizeInBytes = 128 >> 3;
public Aes128Cbc()
: base( AlgorithmName )
{
}
public override ICryptoTransform CreateDecryptor( byte[] key, byte[] iv, byte[] authenticationData, byte[] authenticationTag )
{
if ( key == null )
throw new CryptographicException( "key" );
if ( key.Length < KeySizeInBytes )
throw new CryptographicException( "key", "key must be at least 128 bits" );
return base.CreateDecryptor( key.Take( KeySizeInBytes ), iv, authenticationData, authenticationTag );
}
public override ICryptoTransform CreateEncryptor( byte[] key, byte[] iv, byte[] authenticationData )
{
if ( key == null )
throw new CryptographicException( "key" );
if ( key.Length < KeySizeInBytes )
throw new CryptographicException( "key", "key must be at least 128 bits long" );
return base.CreateEncryptor( key.Take( KeySizeInBytes ), iv, authenticationData );
}
}
/// <summary>
/// AESCBC 192bit key with PKCS7 Padding
/// </summary>
public class Aes192Cbc : AesCbc
{
public const string AlgorithmName = "A192CBC";
const int KeySizeInBytes = 192 >> 3;
public Aes192Cbc()
: base( AlgorithmName )
{
}
public override ICryptoTransform CreateDecryptor( byte[] key, byte[] iv, byte[] authenticationData, byte[] authenticationTag )
{
if ( key == null )
throw new CryptographicException( "key" );
if ( key.Length < KeySizeInBytes )
throw new CryptographicException( "key", "key must be at least 192 bits" );
return base.CreateDecryptor( key.Take( KeySizeInBytes ), iv, authenticationData, authenticationTag );
}
public override ICryptoTransform CreateEncryptor( byte[] key, byte[] iv, byte[] authenticationData )
{
if ( key == null )
throw new CryptographicException( "key" );
if ( key.Length < KeySizeInBytes )
throw new CryptographicException( "key", "key must be at least 192 bits long" );
return base.CreateEncryptor( key.Take( KeySizeInBytes ), iv, authenticationData );
}
}
/// <summary>
/// AESCBC 256bit key with PKCS7 Padding
/// </summary>
public class Aes256Cbc : AesCbc
{
public const string AlgorithmName = "A256CBC";
const int KeySizeInBytes = 256 >> 3;
public Aes256Cbc()
: base( AlgorithmName )
{
}
public override ICryptoTransform CreateDecryptor( byte[] key, byte[] iv, byte[] authenticationData, byte[] authenticationTag )
{
if ( key == null )
throw new CryptographicException( "key" );
if ( key.Length < KeySizeInBytes )
throw new CryptographicException( "key", "key must be at least 256 bits" );
return base.CreateDecryptor( key.Take( KeySizeInBytes ), iv, authenticationData, authenticationTag );
}
public override ICryptoTransform CreateEncryptor( byte[] key, byte[] iv, byte[] authenticationData )
{
if ( key == null )
throw new CryptographicException( "key" );
if ( key.Length < KeySizeInBytes )
throw new CryptographicException( "key", "key must be at least 256 bits long" );
return base.CreateEncryptor( key.Take( KeySizeInBytes ), iv, authenticationData );
}
}
}