DES.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Security / Cryptography / DES.cs / 1305376 / DES.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// [....]
// 
 
//
// DES.cs 
//

namespace System.Security.Cryptography {
    using System; 
    using System.Diagnostics.Contracts;
 
[System.Runtime.InteropServices.ComVisible(true)] 
    public abstract class DES : SymmetricAlgorithm
    { 
        private static  KeySizes[] s_legalBlockSizes = {
            new KeySizes(64, 64, 0)
        };
        private static  KeySizes[] s_legalKeySizes = { 
            new KeySizes(64, 64, 0)
        }; 
 
        //
        // protected constructors 
        //

        protected DES() {
            KeySizeValue = 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 or semi-weak key 
                    do {
                        GenerateKey();
                    } while (IsWeakKey(KeyValue) || IsSemiWeakKey(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 ArgumentException(Environment.GetResourceString("Cryptography_InvalidKeySize"));
                }
                if (IsWeakKey(value)) { 
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKey_Weak"),"DES");
                } 
                if (IsSemiWeakKey(value)) { 
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKey_SemiWeak"),"DES");
                } 
                KeyValue = (byte[]) value.Clone();
                KeySizeValue = value.Length * 8;
            }
        } 

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

        [System.Security.SecuritySafeCritical]  // auto-generated 
        new static public DES Create(String algName) { 
            return (DES) CryptoConfig.CreateFromName(algName);
        } 

        public static bool IsWeakKey(byte[] rgbKey) {
            if (!IsLegalKeySize(rgbKey)) {
                throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKeySize")); 
            }
            byte[] rgbOddParityKey = Utils.FixupKeyParity(rgbKey); 
            UInt64 key = QuadWordFromBigEndian(rgbOddParityKey); 
            if ((key == 0x0101010101010101) ||
                (key == 0xfefefefefefefefe) || 
                (key == 0x1f1f1f1f0e0e0e0e) ||
                (key == 0xe0e0e0e0f1f1f1f1)) {
                return(true);
            } 
            return(false);
        } 
 
        public static bool IsSemiWeakKey(byte[] rgbKey) {
            if (!IsLegalKeySize(rgbKey)) { 
                throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKeySize"));
            }
            byte[] rgbOddParityKey = Utils.FixupKeyParity(rgbKey);
            UInt64 key = QuadWordFromBigEndian(rgbOddParityKey); 
            if ((key == 0x01fe01fe01fe01fe) ||
                (key == 0xfe01fe01fe01fe01) || 
                (key == 0x1fe01fe00ef10ef1) || 
                (key == 0xe01fe01ff10ef10e) ||
                (key == 0x01e001e001f101f1) || 
                (key == 0xe001e001f101f101) ||
                (key == 0x1ffe1ffe0efe0efe) ||
                (key == 0xfe1ffe1ffe0efe0e) ||
                (key == 0x011f011f010e010e) || 
                (key == 0x1f011f010e010e01) ||
                (key == 0xe0fee0fef1fef1fe) || 
                (key == 0xfee0fee0fef1fef1)) { 
                return(true);
            } 
            return(false);
        }

        // 
        // private methods
        // 
 
        private static bool IsLegalKeySize(byte[] rgbKey) {
            if (rgbKey != null && rgbKey.Length == 8) return(true); 
            return(false);
        }

        private static UInt64 QuadWordFromBigEndian(byte[] block) 
        {
            UInt64 x; 
            x =  ( 
                  (((UInt64)block[0]) << 56) | (((UInt64)block[1]) << 48) |
                  (((UInt64)block[2]) << 40) | (((UInt64)block[3]) << 32) | 
                  (((UInt64)block[4]) << 24) | (((UInt64)block[5]) << 16) |
                  (((UInt64)block[6]) << 8) | ((UInt64)block[7])
                  );
            return(x); 
        }
    } 
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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DES.cs source code in C# .NET

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