HMAC.cs source code in C# .NET

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

//
// For test vectors, see RFC2104, e.g. http://www.faqs.org/rfcs/rfc2104.html 
//
 
namespace System.Security.Cryptography { 
    [System.Runtime.InteropServices.ComVisible(true)]
    public abstract class HMAC : KeyedHashAlgorithm { 
        //
        // protected members
        //
 
        // an HMAC uses a hash function where data is hashed by iterating a basic compression
        // function on blocks of data. BlockSizeValue is the byte size of such a block 
 
        private int blockSizeValue = 64;
 
        protected int BlockSizeValue {
            get {
                return blockSizeValue;
            } 
            set {
                blockSizeValue = value; 
            } 
        }
 
        internal string m_hashName;

        internal HashAlgorithm m_hash1;
        internal HashAlgorithm m_hash2; 

        // 
        // private members 
        //
 
        // m_inner = PaddedKey ^ {0x36,...,0x36}
        // m_outer = PaddedKey ^ {0x5C,...,0x5C}
        private byte[] m_inner;
        private byte[] m_outer; 

        private bool m_hashing = false; 
 
        private void UpdateIOPadBuffers () {
            if (m_inner == null) 
                m_inner = new byte[BlockSizeValue];
            if (m_outer == null)
                m_outer = new byte[BlockSizeValue];
 
            int i;
            for (i=0; i < BlockSizeValue; i++) { 
                m_inner[i] = 0x36; 
                m_outer[i] = 0x5C;
            } 
            for (i=0; i < KeyValue.Length; i++) {
                m_inner[i] ^= KeyValue[i];
                m_outer[i] ^= KeyValue[i];
            } 
        }
 
        internal void InitializeKey (byte[] key) { 
            // When we change the key value, we'll need to update the initial values of the inner and outter
            // computation buffers.  In the case of correct HMAC vs Whidbey HMAC, these buffers could get 
            // generated to a different size than when we started.
            m_inner = null;
            m_outer = null;
 
            if (key.Length > BlockSizeValue) {
                KeyValue = m_hash1.ComputeHash(key); 
                // No need to call Initialize, ComputeHash will do it for us 
            } else {
                KeyValue = (byte[]) key.Clone(); 
            }
            UpdateIOPadBuffers();
        }
 
        //
        // public properties 
        // 

        public override byte[] Key { 
            get { return (byte[]) KeyValue.Clone(); }
            set {
                if (m_hashing)
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_HashKeySet")); 
                InitializeKey(value);
            } 
        } 

        public string HashName { 
            get { return m_hashName; }
#if FEATURE_CRYPTO
            [System.Security.SecuritySafeCritical]  // auto-generated
            set { 
                if (m_hashing)
                    throw new CryptographicException(Environment.GetResourceString("Cryptography_HashNameSet")); 
                m_hashName = value; 
                // create the hash algorithms
                m_hash1 = HashAlgorithm.Create(m_hashName); 
                m_hash2 = HashAlgorithm.Create(m_hashName);
            }
#endif // FEATURE_CRYPTO
        } 

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

        [System.Security.SecuritySafeCritical]  // auto-generated 
        new static public HMAC Create (string algorithmName) { 
            return (HMAC) CryptoConfig.CreateFromName(algorithmName);
        } 

        public override void Initialize () {
            m_hash1.Initialize();
            m_hash2.Initialize(); 
            m_hashing = false;
        } 
 
        protected override void HashCore (byte[] rgb, int ib, int cb) {
            if (m_hashing == false) { 
                m_hash1.TransformBlock(m_inner, 0, m_inner.Length, m_inner, 0);
                m_hashing = true;
            }
            m_hash1.TransformBlock(rgb, ib, cb, rgb, ib); 
        }
 
        protected override byte[] HashFinal () { 
            if (m_hashing == false) {
                m_hash1.TransformBlock(m_inner, 0, m_inner.Length, m_inner, 0); 
                m_hashing = true;
            }
            // finalize the original hash
            m_hash1.TransformFinalBlock(new byte[0], 0, 0); 
            byte[] hashValue1 = m_hash1.HashValue;
            // write the outer array 
            m_hash2.TransformBlock(m_outer, 0, m_outer.Length, m_outer, 0); 
            // write the inner hash and finalize the hash
            m_hash2.TransformBlock(hashValue1, 0, hashValue1.Length, hashValue1, 0); 
            m_hashing = false;
            m_hash2.TransformFinalBlock(new byte[0], 0, 0);
            return m_hash2.HashValue;
        } 

        // 
        // IDisposable methods 
        //
 
        protected override void Dispose (bool disposing) {
            if (disposing) {
                if (m_hash1 != null)
                    ((IDisposable)m_hash1).Dispose(); 
                if (m_hash2 != null)
                    ((IDisposable)m_hash2).Dispose(); 
                if (m_inner != null) 
                    Array.Clear(m_inner, 0, m_inner.Length);
                if (m_outer != null) 
                    Array.Clear(m_outer, 0, m_outer.Length);
            }
            // call the base class's Dispose
            base.Dispose(disposing); 
        }
    } 
} 

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

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