1 files changed, 141 insertions, 0 deletions
diff --git a/Crypto/src/crypto/generators/BaseKdfBytesGenerator.cs b/Crypto/src/crypto/generators/BaseKdfBytesGenerator.cs
new file mode 100644
index 000000000..0366401d1
--- /dev/null
+++ b/Crypto/src/crypto/generators/BaseKdfBytesGenerator.cs
@@ -0,0 +1,141 @@
+using System;
+
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Crypto.Parameters;
+
+namespace Org.BouncyCastle.Crypto.Generators
+{
+	/**
+	* Basic KDF generator for derived keys and ivs as defined by IEEE P1363a/ISO 18033
+	* <br/>
+	* This implementation is based on ISO 18033/P1363a.
+	*/
+	public class BaseKdfBytesGenerator
+		: IDerivationFunction
+	{
+		private int     counterStart;
+		private IDigest  digest;
+		private byte[]  shared;
+		private byte[]  iv;
+
+		/**
+		* Construct a KDF Parameters generator.
+		*
+		* @param counterStart value of counter.
+		* @param digest the digest to be used as the source of derived keys.
+		*/
+		protected BaseKdfBytesGenerator(
+			int     counterStart,
+			IDigest  digest)
+		{
+			this.counterStart = counterStart;
+			this.digest = digest;
+		}
+
+		public void Init(
+			IDerivationParameters    parameters)
+		{
+			if (parameters is KdfParameters)
+			{
+				KdfParameters   p = (KdfParameters)parameters;
+
+				shared = p.GetSharedSecret();
+				iv = p.GetIV();
+			}
+			else if (parameters is Iso18033KdfParameters)
+			{
+				Iso18033KdfParameters p = (Iso18033KdfParameters)parameters;
+
+				shared = p.GetSeed();
+				iv = null;
+			}
+			else
+			{
+				throw new ArgumentException("KDF parameters required for KDF Generator");
+			}
+		}
+
+		/**
+		* return the underlying digest.
+		*/
+		public IDigest Digest
+		{
+			get
+			{
+				return digest;
+			}
+		}
+
+		/**
+		* fill len bytes of the output buffer with bytes generated from
+		* the derivation function.
+		*
+		* @throws ArgumentException if the size of the request will cause an overflow.
+		* @throws DataLengthException if the out buffer is too small.
+		*/
+		public int GenerateBytes(
+			byte[]  output,
+			int     outOff,
+			int     length)
+		{
+			if ((output.Length - length) < outOff)
+			{
+				throw new DataLengthException("output buffer too small");
+			}
+
+			long    oBytes = length;
+			int     outLen = digest.GetDigestSize();
+
+			//
+			// this is at odds with the standard implementation, the
+			// maximum value should be hBits * (2^32 - 1) where hBits
+			// is the digest output size in bits. We can't have an
+			// array with a long index at the moment...
+			//
+			if (oBytes > ((2L << 32) - 1))
+			{
+				throw new ArgumentException("Output length too large");
+			}
+
+			int cThreshold = (int)((oBytes + outLen - 1) / outLen);
+
+			byte[] dig = new byte[digest.GetDigestSize()];
+
+			int counter = counterStart;
+
+			for (int i = 0; i < cThreshold; i++)
+			{
+				digest.BlockUpdate(shared, 0, shared.Length);
+
+				digest.Update((byte)(counter >> 24));
+				digest.Update((byte)(counter >> 16));
+				digest.Update((byte)(counter >> 8));
+				digest.Update((byte)counter);
+
+				if (iv != null)
+				{
+					digest.BlockUpdate(iv, 0, iv.Length);
+				}
+
+				digest.DoFinal(dig, 0);
+
+				if (length > outLen)
+				{
+					Array.Copy(dig, 0, output, outOff, outLen);
+					outOff += outLen;
+					length -= outLen;
+				}
+				else
+				{
+					Array.Copy(dig, 0, output, outOff, length);
+				}
+
+				counter++;
+			}
+
+			digest.Reset();
+
+			return (int)oBytes;
+		}
+	}
+}
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