Initial Commit

iTechSharp/srcbc/crypto/CipherKeyGenerator.cs

@@ -0,0 +1,83 @@
+using System;
+
+using Org.BouncyCastle.Security;
+
+namespace Org.BouncyCastle.Crypto
+{
+	/**
+	 * The base class for symmetric, or secret, cipher key generators.
+	 */
+	public class CipherKeyGenerator
+	{
+		protected internal SecureRandom	random;
+		protected internal int			strength;
+		private bool uninitialised = true;
+		private int defaultStrength;
+
+		public CipherKeyGenerator()
+		{
+		}
+
+		internal CipherKeyGenerator(
+			int defaultStrength)
+		{
+			if (defaultStrength < 1)
+				throw new ArgumentException("strength must be a positive value", "defaultStrength");
+
+			this.defaultStrength = defaultStrength;
+		}
+
+		public int DefaultStrength
+		{
+			get { return defaultStrength; }
+		}
+
+		/**
+		 * initialise the key generator.
+		 *
+		 * @param param the parameters to be used for key generation
+		 */
+		public void Init(
+			KeyGenerationParameters parameters)
+		{
+			if (parameters == null)
+				throw new ArgumentNullException("parameters");
+
+			this.uninitialised = false;
+
+			engineInit(parameters);
+		}
+
+		protected virtual void engineInit(
+			KeyGenerationParameters parameters)
+		{
+			this.random = parameters.Random;
+			this.strength = (parameters.Strength + 7) / 8;
+		}
+
+		/**
+		 * Generate a secret key.
+		 *
+		 * @return a byte array containing the key value.
+		 */
+		public byte[] GenerateKey()
+		{
+			if (uninitialised)
+			{
+				if (defaultStrength < 1)
+					throw new InvalidOperationException("Generator has not been initialised");
+
+				uninitialised = false;
+
+				engineInit(new KeyGenerationParameters(new SecureRandom(), defaultStrength));
+			}
+
+			return engineGenerateKey();
+		}
+
+		protected virtual byte[] engineGenerateKey()
+		{
+			return random.GenerateSeed(strength);
+		}
+	}
+}