TripleDES.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Security / Cryptography / TripleDES.cs / 1 / TripleDES.cs
                        

                        
                            // ==++== 
//
//   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"); 
                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
        // 

        new static public TripleDES Create() {
            return Create("System.Security.Cryptography.TripleDES");
        } 

        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"));
            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); 
        }
    } 
}

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