1 files changed, 117 insertions, 0 deletions
diff --git a/Crypto/src/crypto/generators/Mgf1BytesGenerator.cs b/Crypto/src/crypto/generators/Mgf1BytesGenerator.cs
new file mode 100644
index 000000000..23a3aca25
--- /dev/null
+++ b/Crypto/src/crypto/generators/Mgf1BytesGenerator.cs
@@ -0,0 +1,117 @@
+using System;
+//using Org.BouncyCastle.Math;
+//using Org.BouncyCastle.Security;
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Crypto.Parameters;
+
+namespace Org.BouncyCastle.Crypto.Generators
+{
+    /**
+    * Generator for MGF1 as defined in Pkcs 1v2
+    */
+    public class Mgf1BytesGenerator : IDerivationFunction
+    {
+        private IDigest digest;
+        private byte[]  seed;
+        private int     hLen;
+
+        /**
+        * @param digest the digest to be used as the source of Generated bytes
+        */
+        public Mgf1BytesGenerator(
+            IDigest  digest)
+        {
+            this.digest = digest;
+            this.hLen = digest.GetDigestSize();
+        }
+
+        public void Init(
+            IDerivationParameters    parameters)
+        {
+            if (!(typeof(MgfParameters).IsInstanceOfType(parameters)))
+            {
+                throw new ArgumentException("MGF parameters required for MGF1Generator");
+            }
+
+            MgfParameters   p = (MgfParameters)parameters;
+
+            seed = p.GetSeed();
+        }
+
+        /**
+        * return the underlying digest.
+        */
+        public IDigest Digest
+        {
+            get
+            {
+                return digest;
+            }
+        }
+
+        /**
+        * int to octet string.
+        */
+        private void ItoOSP(
+            int     i,
+            byte[]  sp)
+        {
+            sp[0] = (byte)((uint) i >> 24);
+            sp[1] = (byte)((uint) i >> 16);
+            sp[2] = (byte)((uint) i >> 8);
+            sp[3] = (byte)((uint) i >> 0);
+        }
+
+        /**
+        * fill len bytes of the output buffer with bytes Generated from
+        * the derivation function.
+        *
+        * @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");
+			}
+
+			byte[]  hashBuf = new byte[hLen];
+            byte[]  C = new byte[4];
+            int     counter = 0;
+
+            digest.Reset();
+
+			if (length > hLen)
+			{
+				do
+				{
+					ItoOSP(counter, C);
+
+					digest.BlockUpdate(seed, 0, seed.Length);
+					digest.BlockUpdate(C, 0, C.Length);
+					digest.DoFinal(hashBuf, 0);
+
+					Array.Copy(hashBuf, 0, output, outOff + counter * hLen, hLen);
+				}
+				while (++counter < (length / hLen));
+			}
+
+            if ((counter * hLen) < length)
+            {
+                ItoOSP(counter, C);
+
+                digest.BlockUpdate(seed, 0, seed.Length);
+                digest.BlockUpdate(C, 0, C.Length);
+                digest.DoFinal(hashBuf, 0);
+
+                Array.Copy(hashBuf, 0, output, outOff + counter * hLen, length - (counter * hLen));
+            }
+
+            return length;
+        }
+    }
+
+}