mactripleDES.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Security / Cryptography / mactripleDES.cs / 1305376 / mactripleDES.cs
                        
                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// [....]
// 
 
//
// MACTripleDES.cs -- Implementation of the MAC-CBC keyed hash w/ 3DES 
//

// See: http://www.itl.nist.gov/fipspubs/fip81.htm for a spec
 
namespace System.Security.Cryptography {
    using System.IO; 
    using System.Diagnostics.Contracts; 

    [System.Runtime.InteropServices.ComVisible(true)] 
    public class MACTripleDES : KeyedHashAlgorithm
    {
        // Output goes to HashMemorySink since we don't care about the actual data
        private ICryptoTransform m_encryptor; 
        private CryptoStream _cs;
        private TailStream _ts; 
        private const int m_bitsPerByte = 8; 
        private int m_bytesPerBlock;
        private TripleDES des; 

        //
        // public constructors
        // 

        [System.Security.SecuritySafeCritical]  // auto-generated 
        public MACTripleDES() { 
            KeyValue = new byte[24];
            Utils.StaticRandomNumberGenerator.GetBytes(KeyValue); 

            // Create a TripleDES encryptor
            des = TripleDES.Create();
            HashSizeValue = des.BlockSize; 

            m_bytesPerBlock = des.BlockSize/m_bitsPerByte; 
            // By definition, MAC-CBC-3DES takes an IV=0.  C# zero-inits arrays, 
            // so all we have to do here is define it.
            des.IV = new byte[m_bytesPerBlock]; 
            des.Padding = PaddingMode.Zeros;

            m_encryptor = null;
        } 

        [System.Security.SecuritySafeCritical]  // auto-generated 
        public MACTripleDES(byte[] rgbKey) 
            : this("System.Security.Cryptography.TripleDES",rgbKey) {}
 
        [System.Security.SecuritySafeCritical]  // auto-generated
        public MACTripleDES(String strTripleDES, byte[] rgbKey) {
            // Make sure we know which algorithm to use
            if (rgbKey == null) 
                throw new ArgumentNullException("rgbKey");
            Contract.EndContractBlock(); 
            // Create a TripleDES encryptor 
            if (strTripleDES == null) {
                des = TripleDES.Create(); 
            } else {
                des = TripleDES.Create(strTripleDES);
            }
 
            HashSizeValue = des.BlockSize;
            // Stash the key away 
            KeyValue = (byte[]) rgbKey.Clone(); 

            m_bytesPerBlock = des.BlockSize/m_bitsPerByte; 
            // By definition, MAC-CBC-3DES takes an IV=0.  C# zero-inits arrays,
            // so all we have to do here is define it.
            des.IV = new byte[m_bytesPerBlock];
            des.Padding = PaddingMode.Zeros; 

            m_encryptor = null; 
        } 

        public override void Initialize() { 
            m_encryptor = null;
        }

        [System.Runtime.InteropServices.ComVisible(false)] 
        public PaddingMode Padding {
            get { return des.Padding; } 
            set { 
                if ((value < PaddingMode.None) || (PaddingMode.ISO10126 < value))
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_InvalidPaddingMode")); 
                des.Padding = value;
            }
        }
 
        //
        // protected methods 
        // 

        protected override void HashCore(byte[] rgbData, int ibStart, int cbSize) { 
            // regenerate the TripleDES object before each call to ComputeHash
            if (m_encryptor == null) {
                des.Key = this.Key;
                m_encryptor = des.CreateEncryptor(); 
                _ts = new TailStream(des.BlockSize / 8); // 8 bytes
                _cs = new CryptoStream(_ts, m_encryptor, CryptoStreamMode.Write); 
            } 

            // Encrypt using 3DES 
            _cs.Write(rgbData, ibStart, cbSize);
        }

        protected override byte[] HashFinal() { 
            // If Hash has been called on a zero buffer
            if (m_encryptor == null) { 
                des.Key = this.Key; 
                m_encryptor = des.CreateEncryptor();
                _ts = new TailStream(des.BlockSize / 8); // 8 bytes 
                _cs = new CryptoStream(_ts, m_encryptor, CryptoStreamMode.Write);
            }

            // Finalize the hashing and return the result 
            _cs.FlushFinalBlock();
            return _ts.Buffer; 
        } 

        // IDisposable methods 
        protected override void Dispose(bool disposing) {
            if (disposing) {
                // dispose of our internal state
                if (des != null) 
                    des.Clear();
                if (m_encryptor != null) 
                    m_encryptor.Dispose(); 
                if (_cs != null)
                    _cs.Clear(); 
                if (_ts != null)
                    _ts.Clear();
            }
            base.Dispose(disposing); 
        }
    } 
 
    //
    // TailStream is another utility class -- it remembers the last n bytes written to it 
    // This is useful for MAC-3DES since we need to capture only the result of the last block

    internal sealed class TailStream : Stream {
        private byte[] _Buffer; 
        private int _BufferSize;
        private int _BufferIndex = 0; 
        private bool _BufferFull = false; 

        public TailStream(int bufferSize) { 
            _Buffer = new byte[bufferSize];
            _BufferSize = bufferSize;
        }
 
        public void Clear() {
            Close(); 
        } 

        protected override void Dispose(bool disposing) { 
            try {
                if (disposing) {
                    if (_Buffer != null) {
                        Array.Clear(_Buffer, 0, _Buffer.Length); 
                    }
                    _Buffer = null; 
                } 
            }
            finally { 
                base.Dispose(disposing);
            }
        }
 
        public byte[] Buffer {
            get { return (byte[]) _Buffer.Clone(); } 
        } 

        public override bool CanRead { 
            [Pure]
            get { return false; }
        }
 
        public override bool CanSeek {
            [Pure] 
            get { return false; } 
        }
 
        public override bool CanWrite {
            [Pure]
            get { return _Buffer != null; }
        } 

        public override long Length { 
            get { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); } 
        }
 
        public override long Position {
            get { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); }
            set { throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); }
        } 

        public override void Flush() { 
            return; 
        }
 
        public override long Seek(long offset, SeekOrigin origin) {
            throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream"));
        }
 
        public override void SetLength(long value) {
            throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnseekableStream")); 
        } 

        public override int Read(byte[] buffer, int offset, int count) { 
            throw new NotSupportedException(Environment.GetResourceString("NotSupported_UnreadableStream"));
        }

        [System.Security.SecuritySafeCritical]  // auto-generated 
        public override void Write(byte[] buffer, int offset, int count) {
            if (_Buffer == null) 
                throw new ObjectDisposedException("TailStream"); 

            // If no bytes to write, then return 
            if (count == 0) return;
            // The most common case will be when we have a full buffer
            if (_BufferFull) {
                // if more bytes are written in this call than the size of the buffer, 
                // just remember the last _BufferSize bytes
                if (count > _BufferSize) { 
                    System.Buffer.InternalBlockCopy(buffer, offset+count-_BufferSize, _Buffer, 0, _BufferSize); 
                    return;
                } else { 
                    // move _BufferSize - count bytes left, then copy the new bytes
                    System.Buffer.InternalBlockCopy(_Buffer, _BufferSize - count, _Buffer, 0, _BufferSize - count);
                    System.Buffer.InternalBlockCopy(buffer, offset, _Buffer, _BufferSize - count, count);
                    return; 
                }
            } else { 
                // buffer isn't full yet, so more cases 
                if (count > _BufferSize) {
                    System.Buffer.InternalBlockCopy(buffer, offset+count-_BufferSize, _Buffer, 0, _BufferSize); 
                    _BufferFull = true;
                    return;
                } else if (count + _BufferIndex >= _BufferSize) {
                    System.Buffer.InternalBlockCopy(_Buffer, _BufferIndex+count-_BufferSize, _Buffer, 0, _BufferSize - count); 
                    System.Buffer.InternalBlockCopy(buffer, offset, _Buffer, _BufferIndex, count);
                    _BufferFull = true; 
                    return; 
                } else {
                    System.Buffer.InternalBlockCopy(buffer, offset, _Buffer, _BufferIndex, count); 
                    _BufferIndex += count;
                    return;
                }
            } 
        }
    } 
} 

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

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