// <auto-generated />

//
// DiffieHellmanManaged.cs: Implements the Diffie-Hellman key agreement algorithm
//
// Author:
//	Pieter Philippaerts (Pieter@mentalis.org)
//
// (C) 2003 The Mentalis.org Team (http://www.mentalis.org/)
//
//   References:
//     - PKCS#3  [http://www.rsasecurity.com/rsalabs/pkcs/pkcs-3/]
//
//
// Source Code License
// Copyright © 2002-2007, The Mentalis.org Team
// All rights reserved.
// http://www.mentalis.org/
// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
// - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 
// - Neither the name of the Mentalis.org Team, nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

using System;
using System.Security.Cryptography;
using Mono.Math;

namespace Org.Mentalis.Security.Cryptography {
	/// <summary>
	/// Implements the Diffie-Hellman algorithm.
	/// </summary>
	internal sealed class DiffieHellmanManaged : DiffieHellman {
		/// <summary>
		/// Initializes a new <see cref="DiffieHellmanManaged"/> instance.
		/// </summary>
		/// <remarks>The default length of the shared secret is 1024 bits.</remarks>
		public DiffieHellmanManaged() : this(1024, 160, DHKeyGeneration.Static) {}
		/// <summary>
		/// Initializes a new <see cref="DiffieHellmanManaged"/> instance.
		/// </summary>
		/// <param name="bitlen">The length, in bits, of the public P parameter.</param>
		/// <param name="l">The length, in bits, of the secret value X. This parameter can be set to 0 to use the default size.</param>
		/// <param name="keygen">One of the <see cref="DHKeyGeneration"/> values.</param>
		/// <remarks>The larger the bit length, the more secure the algorithm is. The default is 1024 bits. The minimum bit length is 128 bits.<br/>The size of the private value will be one fourth of the bit length specified.</remarks>
		/// <exception cref="ArgumentException">The specified bit length is invalid.</exception>
		public DiffieHellmanManaged(int bitlen, int l, DHKeyGeneration keygen) {
			if (bitlen < 256 || l < 0)
				throw new ArgumentException();
			BigInteger p, g;
			GenerateKey(bitlen, keygen, out p, out g);
			Initialize(p, g, null, l, false);
		}
		/// <summary>
		/// Initializes a new <see cref="DiffieHellmanManaged"/> instance.
		/// </summary>
		/// <param name="p">The P parameter of the Diffie-Hellman algorithm. This is a public parameter.</param>
		/// <param name="g">The G parameter of the Diffie-Hellman algorithm. This is a public parameter.</param>
		/// <param name="x">The X parameter of the Diffie-Hellman algorithm. This is a private parameter. If this parameters is a null reference (<b>Nothing</b> in Visual Basic), a secret value of the default size will be generated.</param>
		/// <exception cref="ArgumentNullException"><paramref name="p"/> or <paramref name="g"/> is a null reference (<b>Nothing</b> in Visual Basic).</exception>
		/// <exception cref="CryptographicException"><paramref name="p"/> or <paramref name="g"/> is invalid.</exception>
		public DiffieHellmanManaged(byte[] p, byte[] g, byte[] x) {
			if (p == null || g == null)
				throw new ArgumentNullException();
			if (x == null)
				Initialize(new BigInteger(p), new BigInteger(g), null, 0, true);
			else
				Initialize(new BigInteger(p), new BigInteger(g), new BigInteger(x), 0, true);
		}
		/// <summary>
		/// Initializes a new <see cref="DiffieHellmanManaged"/> instance.
		/// </summary>
		/// <param name="p">The P parameter of the Diffie-Hellman algorithm.</param>
		/// <param name="g">The G parameter of the Diffie-Hellman algorithm.</param>
		/// <param name="l">The length, in bits, of the private value. If 0 is specified, the default value will be used.</param>
		/// <exception cref="ArgumentNullException"><paramref name="p"/> or <paramref name="g"/> is a null reference (<b>Nothing</b> in Visual Basic).</exception>
		/// <exception cref="ArgumentException"><paramref name="l"/> is invalid.</exception>
		/// <exception cref="CryptographicException"><paramref name="p"/> or <paramref name="g"/> is invalid.</exception>
		public DiffieHellmanManaged(byte[] p, byte[] g, int l) {
			if (p == null || g == null)
				throw new ArgumentNullException();
			if (l < 0)
				throw new ArgumentException();
			Initialize(new BigInteger(p), new BigInteger(g), null, l, true);
		}

		// initializes the private variables (throws CryptographicException)
		private void Initialize(BigInteger p, BigInteger g, BigInteger x, int secretLen, bool checkInput) {
			if (!p.isProbablePrime() || g <= 0 || g >= p || (x != null && (x <= 0 || x > p - 2)))
				throw new CryptographicException();
			// default is to generate a number as large as the prime this
			// is usually overkill, but it's the most secure thing we can
			// do if the user doesn't specify a desired secret length ...
			if (secretLen == 0)
				secretLen = p.bitCount();
			m_P = p;
			m_G = g;
			if (x == null) {
				BigInteger pm1 = m_P - 1;
				for(m_X = BigInteger.genRandom(secretLen); m_X >= pm1 || m_X == 0; m_X = BigInteger.genRandom(secretLen)) {}
			} else {
				m_X = x;
			}
		}
		/// <summary>
		/// Creates the key exchange data.
		/// </summary>
		/// <returns>The key exchange data to be sent to the intended recipient.</returns>
		public override byte[] CreateKeyExchange() {
			BigInteger y = m_G.modPow(m_X, m_P);
			byte[] ret = y.getBytes();
			y.Clear();
			return ret;
		}
		/// <summary>
		/// Extracts secret information from the key exchange data.
		/// </summary>
		/// <param name="keyEx">The key exchange data within which the shared key is hidden.</param>
		/// <returns>The shared key derived from the key exchange data.</returns>
		public override byte[] DecryptKeyExchange(byte[] keyEx) {
			BigInteger pvr = new BigInteger(keyEx);
			BigInteger z = pvr.modPow(m_X, m_P);
			byte[] ret = z.getBytes();
			z.Clear();
			return ret;
		}
		/// <summary>
		/// Gets the name of the key exchange algorithm.
		/// </summary>
		/// <value>The name of the key exchange algorithm.</value>
		public override string KeyExchangeAlgorithm {
			get {
				return "1.2.840.113549.1.3"; // PKCS#3 OID
			}
		}
		/// <summary>
		/// Gets the name of the signature algorithm.
		/// </summary>
		/// <value>The name of the signature algorithm.</value>
		public override string SignatureAlgorithm {
			get {
				return null;
			}
		}
		/// <summary>
		/// Releases the unmanaged resources used by the SymmetricAlgorithm and optionally releases the managed resources.
		/// </summary>
		/// <param name="disposing"><b>true</b> to release both managed and unmanaged resources; <b>false</b> to release only unmanaged resources.</param>
		protected override void Dispose(bool disposing) {
			if (!m_Disposed) {
				m_P.Clear();
				m_G.Clear();
				m_X.Clear();
			}
			m_Disposed = true;
		}
		/// <summary>
		/// Exports the <see cref="DHParameters"/>.
		/// </summary>
		/// <param name="includePrivateParameters"><b>true</b> to include private parameters; otherwise, <b>false</b>.</param>
		/// <returns>The parameters for <see cref="DiffieHellman"/>.</returns>
		public override DHParameters ExportParameters(bool includePrivateParameters) {
			DHParameters ret = new DHParameters();
			ret.P = m_P.getBytes();
			ret.G = m_G.getBytes();
			if (includePrivateParameters) {
				ret.X = m_X.getBytes();
			}
			return ret;
		}
		/// <summary>
		/// Imports the specified <see cref="DHParameters"/>.
		/// </summary>
		/// <param name="parameters">The parameters for <see cref="DiffieHellman"/>.</param>
		/// <exception cref="CryptographicException"><see cref="DHParameters.P">parameters.P</see> or <see cref="DHParameters.G">parameters.G</see> is a null reference (<b>Nothing</b> in Visual Basic) -or- <see cref="DHParameters.P">parameters.P</see> is not a prime number.</exception>
		public override void ImportParameters(DHParameters parameters) {
			if (parameters.P == null)
				throw new CryptographicException("Missing P value.");
			if (parameters.G == null)
				throw new CryptographicException("Missing G value.");

			BigInteger p = new BigInteger(parameters.P), g = new BigInteger(parameters.G), x = null;
			if (parameters.X != null) {
				x = new BigInteger(parameters.X);
			}
			Initialize(p, g, x, 0, true);
		}
		/// <summary>
		/// Releases the unmanaged resources used by the SymmetricAlgorithm.
		/// </summary>
		~DiffieHellmanManaged() {
			Dispose(false);
		}

		//TODO: implement DH key generation methods
		private void GenerateKey(int bitlen, DHKeyGeneration keygen, out BigInteger p, out BigInteger g) {
			if (keygen == DHKeyGeneration.Static) {
				if (bitlen == 768)
					p = new BigInteger(m_OAKLEY768);
				else if (bitlen == 1024)
					p = new BigInteger(m_OAKLEY1024);
				else if (bitlen == 1536)
					p = new BigInteger(m_OAKLEY1536);
				else
					throw new ArgumentException("Invalid bit size.");
				g = new BigInteger(22); // all OAKLEY keys use 22 as generator
			//} else if (keygen == DHKeyGeneration.SophieGermain) {
			//	throw new NotSupportedException(); //TODO
			//} else if (keygen == DHKeyGeneration.DSA) {
				// 1. Let j = (p - 1)/q.
				// 2. Set h = any integer, where 1 < h < p - 1
				// 3. Set g = h^j mod p
				// 4. If g = 1 go to step 2
			//	BigInteger j = (p - 1) / q;
			} else { // random
				p = BigInteger.genPseudoPrime(bitlen);
				g = new BigInteger(3); // always use 3 as a generator
			}
		}

		private BigInteger m_P;
		private BigInteger m_G;
		private BigInteger m_X;
		private bool m_Disposed;

		private byte[] m_OAKLEY768 = new byte[] {
													0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,
													0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
													0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
													0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
													0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,
													0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
													0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
													0xA6, 0x3A, 0x36, 0x20, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
												};
		private byte[] m_OAKLEY1024 = new byte[] {
													 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,
													 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
													 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
													 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
													 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,
													 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
													 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
													 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,
													 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,
													 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81,
													 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
												 };
		private byte[] m_OAKLEY1536 = new byte[] {
													 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,
													 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,
													 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,
													 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,
													 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,
													 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,
													 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
													 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,
													 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,
													 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE4, 0x5B, 0x3D,
													 0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05, 0x98, 0xDA, 0x48, 0x36,
													 0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F,
													 0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3, 0x56,
													 0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96, 0x6D,
													 0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C, 0x08,
													 0xCA, 0x23, 0x73, 0x27, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
												 };
	}
}