SymmetricAlgorithm.cs source code in C# .NET

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

// 
// SymmetricAlgorithm.cs
//

namespace System.Security.Cryptography { 
[System.Runtime.InteropServices.ComVisible(true)]
    public abstract class SymmetricAlgorithm : IDisposable { 
        protected int         BlockSizeValue; 
        protected int         FeedbackSizeValue;
        protected byte[]      IVValue; 
        protected byte[]      KeyValue;
        protected KeySizes[]  LegalBlockSizesValue;
        protected KeySizes[]  LegalKeySizesValue;
        protected int         KeySizeValue; 
        protected CipherMode  ModeValue;
        protected PaddingMode PaddingValue; 
 
        //
        // protected constructors 
        //

        protected SymmetricAlgorithm() {
            // Default to cipher block chaining (CipherMode.CBC) and 
            // PKCS-style padding (pad n bytes with value n)
            ModeValue = CipherMode.CBC; 
            PaddingValue = PaddingMode.PKCS7; 
        }
 
        // SymmetricAlgorithm implements IDisposable

        // To keep mscorlib compatibility with Orcas, CoreCLR's SymmetricAlgorithm has an explicit IDisposable
        // implementation. Post-Orcas the desktop has an implicit IDispoable implementation. 
#if FEATURE_CORECLR
        void IDisposable.Dispose() 
#if false 
        { }
#endif // false 
#else
        [System.Security.SecuritySafeCritical]  // auto-generated
        public void Dispose()
#endif // FEATURE_CORECLR 
        {
            Dispose(true); 
            GC.SuppressFinalize(this); 
        }
 
        public void Clear() {
            (this as IDisposable).Dispose();
        }
 
        protected virtual void Dispose(bool disposing) {
            if (disposing) { 
                // Note: we always want to zeroize the sensitive key material 
                if (KeyValue != null) {
                    Array.Clear(KeyValue, 0, KeyValue.Length); 
                    KeyValue = null;
                }
                if (IVValue != null) {
                    Array.Clear(IVValue, 0, IVValue.Length); 
                    IVValue = null;
                } 
            } 
        }
 
        //
        // public properties
        //
 
        public virtual int BlockSize {
            get { return BlockSizeValue; } 
            set { 
                int   i;
                int   j; 

                for (i=0; i BlockSizeValue || (value % 8) != 0)
                   throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidFeedbackSize")); 

               FeedbackSizeValue = value; 
            } 
        }
 
        public virtual byte[] IV {
            get {
                if (IVValue == null) GenerateIV();
                return (byte[]) IVValue.Clone(); 
            }
            set { 
                if (value == null) throw new ArgumentNullException("value"); 
                Contract.EndContractBlock();
                if (value.Length != BlockSizeValue / 8) 
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidIVSize"));

                IVValue = (byte[]) value.Clone();
            } 
        }
 
        public virtual byte[] Key { 
            get {
                if (KeyValue == null) GenerateKey(); 
                return (byte[]) KeyValue.Clone();
            }
            set {
                if (value == null) throw new ArgumentNullException("value"); 
                Contract.EndContractBlock();
                if (!ValidKeySize(value.Length * 8)) 
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKeySize")); 

                // must convert bytes to bits 
                KeyValue = (byte[]) value.Clone();
                KeySizeValue = value.Length * 8;
            }
        } 

        public virtual KeySizes[] LegalBlockSizes { 
            get { return (KeySizes[]) LegalBlockSizesValue.Clone(); } 
        }
 
        public virtual KeySizes[] LegalKeySizes {
            get { return (KeySizes[]) LegalKeySizesValue.Clone(); }
        }
 
        public virtual int KeySize {
            get { return KeySizeValue; } 
            set { 
                if (!ValidKeySize(value))
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidKeySize")); 

                KeySizeValue = value;
                KeyValue = null;
            } 
        }
 
        public virtual CipherMode Mode { 
            get { return ModeValue; }
            set { 
                if ((value < CipherMode.CBC) || (CipherMode.CFB < value))
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidCipherMode"));

                ModeValue = value; 
            }
        } 
 
        public virtual PaddingMode Padding {
            get { return PaddingValue; } 
            set {
                if ((value < PaddingMode.None) || (PaddingMode.ISO10126 < value))
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidPaddingMode"));
 
                PaddingValue = value;
            } 
        } 

        // 
        // public methods
        //

        // The following method takes a bit length input and returns whether that length is a valid size 
        // according to LegalKeySizes
        public bool ValidKeySize(int bitLength) { 
            KeySizes[] validSizes = this.LegalKeySizes; 
            int i,j;
 
            if (validSizes == null) return false;
            for (i=0; i< validSizes.Length; i++) {
                if (validSizes[i].SkipSize == 0) {
                    if (validSizes[i].MinSize == bitLength) { // assume MinSize = MaxSize 
                        return true;
                    } 
                } else { 
                    for (j = validSizes[i].MinSize; j<= validSizes[i].MaxSize;
                         j += validSizes[i].SkipSize) { 
                        if (j == bitLength) {
                            return true;
                        }
                    } 
                }
            } 
            return false; 
        }
 
        [System.Security.SecuritySafeCritical]  // auto-generated
        static public SymmetricAlgorithm Create() {
            // use the crypto config system to return an instance of
            // the default SymmetricAlgorithm on this machine 
            return Create("System.Security.Cryptography.SymmetricAlgorithm");
        } 
 
        [System.Security.SecuritySafeCritical]  // auto-generated
        static public SymmetricAlgorithm Create(String algName) { 
            return (SymmetricAlgorithm) CryptoConfig.CreateFromName(algName);
        }

        public virtual ICryptoTransform CreateEncryptor() { 
            return CreateEncryptor(Key, IV);
        } 
 
        public abstract ICryptoTransform CreateEncryptor(byte[] rgbKey, byte[] rgbIV);
 
        public virtual ICryptoTransform CreateDecryptor() {
            return CreateDecryptor(Key, IV);
        }
 
        public abstract ICryptoTransform CreateDecryptor(byte[] rgbKey, byte[] rgbIV);
 
        public abstract void GenerateKey(); 

        public abstract void GenerateIV(); 
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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SymmetricAlgorithm.cs source code in C# .NET

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