TripleDES.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Security / Cryptography / TripleDES.cs / 1305376 / TripleDES.cs
                        

                        
                            using System.Diagnostics.Contracts; 
// ==++==
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==
// [....] 
// 

// 
// TripleDES.cs
//

namespace System.Security.Cryptography { 
[System.Runtime.InteropServices.ComVisible(true)]
    public abstract class TripleDES : SymmetricAlgorithm 
    { 
        private static  KeySizes[] s_legalBlockSizes = {
            new KeySizes(64, 64, 0) 
        };

        private static  KeySizes[] s_legalKeySizes = {
            new KeySizes(2*64, 3*64, 64) 
        };
 
        // 
        // protected constructors
        // 

        protected TripleDES() {
            KeySizeValue = 3*64;
            BlockSizeValue = 64; 
            FeedbackSizeValue = BlockSizeValue;
            LegalBlockSizesValue = s_legalBlockSizes; 
            LegalKeySizesValue = s_legalKeySizes; 
        }
 
        //
        // public properties
        //
 
        public override byte[] Key {
            get { 
                if (KeyValue == null) { 
                    // Never hand back a weak key
                    do { 
                        GenerateKey();
                    } while (IsWeakKey(KeyValue));
                }
                return (byte[]) KeyValue.Clone(); 
            }
            set { 
                if (value == null) throw new ArgumentNullException("value"); 
                Contract.EndContractBlock();
                if (!ValidKeySize(value.Length * 8)) { // must convert bytes to bits 
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKeySize"));
                }
                if (IsWeakKey(value)) {
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKey_Weak"),"TripleDES"); 
                }
                KeyValue = (byte[]) value.Clone(); 
                KeySizeValue = value.Length * 8; 
            }
        } 

        //
        // public methods
        // 

        [System.Security.SecuritySafeCritical]  // auto-generated 
        new static public TripleDES Create() { 
            return Create("System.Security.Cryptography.TripleDES");
        } 

        [System.Security.SecuritySafeCritical]  // auto-generated
        new static public TripleDES Create(String str) {
            return (TripleDES) CryptoConfig.CreateFromName(str); 
        }
 
        public static bool IsWeakKey(byte[] rgbKey) { 
            // All we have to check for here is (a) we're in 3-key mode (192 bits), and
            // (b) either K1 == K2 or K2 == K3 
            if (!IsLegalKeySize(rgbKey)) {
                throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKeySize"));
            }
            byte[] rgbOddParityKey = Utils.FixupKeyParity(rgbKey); 
            if (EqualBytes(rgbOddParityKey,0,8,8)) return(true);
            if ((rgbOddParityKey.Length == 24) && EqualBytes(rgbOddParityKey,8,16,8)) return(true); 
            return(false); 
        }
 
        //
        // private methods
        //
 
        private static bool EqualBytes(byte[] rgbKey, int start1, int start2, int count) {
            if (start1 < 0) throw new ArgumentOutOfRangeException("start1", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
            if (start2 < 0) throw new ArgumentOutOfRangeException("start2", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); 
            if ((start1+count) > rgbKey.Length) throw new ArgumentException(Environment.GetResourceString("Argument_InvalidValue"));
            if ((start2+count) > rgbKey.Length) throw new ArgumentException(Environment.GetResourceString("Argument_InvalidValue")); 
            Contract.EndContractBlock();
            for (int i = 0; i < count; i++) {
                if (rgbKey[start1+i] != rgbKey[start2+i]) return(false);
            } 
            return(true);
        } 
 
        private static bool IsLegalKeySize(byte[] rgbKey) {
            if (rgbKey != null && ((rgbKey.Length == 16) || (rgbKey.Length == 24))) 
                return(true);
            return(false);
        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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