DESCryptoServiceProvider.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 / DESCryptoServiceProvider.cs / 1305376 / DESCryptoServiceProvider.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// [....]
// 
 
//
// DESCryptoServiceProvider.cs 
//

namespace System.Security.Cryptography {
    [System.Runtime.InteropServices.ComVisible(true)] 
    public sealed class DESCryptoServiceProvider : DES {
        // 
        // public constructors 
        //
 
        [System.Security.SecuritySafeCritical]  // auto-generated
        public DESCryptoServiceProvider () {
            if (!Utils.HasAlgorithm(Constants.CALG_DES, 0))
                throw new CryptographicException(Environment.GetResourceString("Cryptography_CSP_AlgorithmNotAvailable")); 
            // Since the CSP only supports a CFB feedback of 8, make that the default
            FeedbackSizeValue = 8; 
        } 

        // 
        // public methods
        //

        [System.Security.SecuritySafeCritical]  // auto-generated 
        public override ICryptoTransform CreateEncryptor (byte[] rgbKey, byte[] rgbIV) {
            if (IsWeakKey(rgbKey)) 
                throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKey_Weak"),"DES"); 
            if (IsSemiWeakKey(rgbKey))
                throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKey_SemiWeak"),"DES"); 

            return _NewEncryptor(rgbKey, ModeValue, rgbIV, FeedbackSizeValue, CryptoAPITransformMode.Encrypt);
        }
 
        [System.Security.SecuritySafeCritical]  // auto-generated
        public override ICryptoTransform CreateDecryptor (byte[] rgbKey, byte[] rgbIV) { 
            if (IsWeakKey(rgbKey)) 
                throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKey_Weak"),"DES");
            if (IsSemiWeakKey(rgbKey)) 
                throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKey_SemiWeak"),"DES");

            return _NewEncryptor(rgbKey, ModeValue, rgbIV, FeedbackSizeValue, CryptoAPITransformMode.Decrypt);
        } 

        public override void GenerateKey () { 
            KeyValue = new byte[8]; 
            Utils.StaticRandomNumberGenerator.GetBytes(KeyValue);
            // Never hand back a weak or semi-weak key 
            while (DES.IsWeakKey(KeyValue) || DES.IsSemiWeakKey(KeyValue)) {
                Utils.StaticRandomNumberGenerator.GetBytes(KeyValue);
            }
        } 

        public override void GenerateIV () { 
            IVValue = new byte[8]; 
            Utils.StaticRandomNumberGenerator.GetBytes(IVValue);
        } 

        //
        // private methods
        // 

        [System.Security.SecurityCritical]  // auto-generated 
        private ICryptoTransform _NewEncryptor (byte[] rgbKey, CipherMode mode, byte[] rgbIV, int feedbackSize, CryptoAPITransformMode encryptMode) { 
            int cArgs = 0;
            int[] rgArgIds = new int[10]; 
            Object[] rgArgValues = new Object[10];

            // Check for bad values
            // 1) we don't support OFB mode in DESCryptoServiceProvider 
            if (mode == CipherMode.OFB)
                throw new CryptographicException(Environment.GetResourceString("Cryptography_CSP_OFBNotSupported")); 
            // 2) we only support CFB with a feedback size of 8 bits 
            if ((mode == CipherMode.CFB) && (feedbackSize != 8))
                throw new CryptographicException(Environment.GetResourceString("Cryptography_CSP_CFBSizeNotSupported")); 

            // Build the key if one does not already exist
            if (rgbKey == null) {
                rgbKey = new byte[8]; 
                Utils.StaticRandomNumberGenerator.GetBytes(rgbKey);
            } 
 
            // Set the mode for the encryptor (defaults to CBC)
            if (mode != CipherMode.CBC) { 
                rgArgIds[cArgs] = Constants.KP_MODE;
                rgArgValues[cArgs] = mode;
                cArgs += 1;
            } 

            // If not ECB mode -- pass in an IV 
            if (mode != CipherMode.ECB) { 
                if (rgbIV == null) {
                    rgbIV = new byte[8]; 
                    Utils.StaticRandomNumberGenerator.GetBytes(rgbIV);
                }

                // 
                // We truncate IV's that are longer than the block size to 8 bytes : this is
                // done to maintain backward compatibility with the behavior shipped in V1.x. 
                // The call to set the IV in CryptoAPI will ignore any bytes after the first 8 
                // bytes. We'll still reject IV's that are shorter than the block size though.
                // 
                if (rgbIV.Length < 8)
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidIVSize"));

                rgArgIds[cArgs] = Constants.KP_IV; 
                rgArgValues[cArgs] = rgbIV;
                cArgs += 1; 
            } 

            // If doing OFB or CFB, then we need to set the feed back loop size 
            if ((mode == CipherMode.OFB) || (mode == CipherMode.CFB)) {
                rgArgIds[cArgs] = Constants.KP_MODE_BITS;
                rgArgValues[cArgs] = feedbackSize;
                cArgs += 1; 
            }
 
            // Create the encryptpr/decryptor object 
            return new CryptoAPITransform(Constants.CALG_DES, cArgs, rgArgIds,
                                          rgArgValues, rgbKey, PaddingValue, 
                                          mode, BlockSizeValue, feedbackSize, false,
                                          encryptMode);
        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

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