119 lines
3.9 KiB
C#
119 lines
3.9 KiB
C#
//
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// TripleDESCryptoServiceProvider.cs: Default TripleDES implementation
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//
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// Author:
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// Sebastien Pouliot <sebastien@ximian.com>
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//
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// (C) 2002 Motus Technologies Inc. (http://www.motus.com)
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// Copyright (C) 2004-2005 Novell, Inc (http://www.novell.com)
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//
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// Permission is hereby granted, free of charge, to any person obtaining
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// a copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to
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// permit persons to whom the Software is furnished to do so, subject to
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// the following conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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//
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using System.Runtime.InteropServices;
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using Mono.Security.Cryptography;
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namespace System.Security.Cryptography {
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// References:
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// a. FIPS PUB 46-3: TripleDES
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// http://csrc.nist.gov/publications/fips/fips46-3/fips46-3.pdf
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// b. ANSI X9.52
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// not free :-(
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// http://webstore.ansi.org/ansidocstore/product.asp?sku=ANSI+X9%2E52%2D1998
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// TripleDES is just DES-EDE
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internal class TripleDESTransform : SymmetricTransform {
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// for encryption
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private DESTransform E1;
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private DESTransform D2;
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private DESTransform E3;
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// for decryption
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private DESTransform D1;
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private DESTransform E2;
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private DESTransform D3;
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public TripleDESTransform (TripleDES algo, bool encryption, byte[] key, byte[] iv) : base (algo, encryption, iv)
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{
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if (key == null) {
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key = GetStrongKey ();
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}
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// note: checking weak keys also checks valid key length
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if (TripleDES.IsWeakKey (key)) {
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string msg = Locale.GetText ("This is a known weak key.");
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throw new CryptographicException (msg);
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}
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byte[] key1 = new byte [8];
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byte[] key2 = new byte [8];
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byte[] key3 = new byte [8];
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DES des = DES.Create ();
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Buffer.BlockCopy (key, 0, key1, 0, 8);
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Buffer.BlockCopy (key, 8, key2, 0, 8);
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if (key.Length == 16)
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Buffer.BlockCopy (key, 0, key3, 0, 8);
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else
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Buffer.BlockCopy (key, 16, key3, 0, 8);
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// note: some modes (like CFB) requires encryption when decrypting
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if ((encryption) || (algo.Mode == CipherMode.CFB)) {
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E1 = new DESTransform (des, true, key1, iv);
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D2 = new DESTransform (des, false, key2, iv);
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E3 = new DESTransform (des, true, key3, iv);
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}
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else {
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D1 = new DESTransform (des, false, key3, iv);
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E2 = new DESTransform (des, true, key2, iv);
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D3 = new DESTransform (des, false, key1, iv);
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}
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}
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// note: this method is garanteed to be called with a valid blocksize
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// for both input and output
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protected override void ECB (byte[] input, byte[] output)
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{
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DESTransform.Permutation (input, output, DESTransform.ipTab, false);
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if (encrypt) {
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E1.ProcessBlock (output, output);
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D2.ProcessBlock (output, output);
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E3.ProcessBlock (output, output);
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}
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else {
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D1.ProcessBlock (output, output);
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E2.ProcessBlock (output, output);
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D3.ProcessBlock (output, output);
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}
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DESTransform.Permutation (output, output, DESTransform.fpTab, true);
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}
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static internal byte[] GetStrongKey ()
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{
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int size = DESTransform.BLOCK_BYTE_SIZE * 3;
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byte[] key = KeyBuilder.Key (size);
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while (TripleDES.IsWeakKey (key))
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key = KeyBuilder.Key (size);
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return key;
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}
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}
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}
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