1 files changed, 58 insertions, 0 deletions
diff --git a/crypto/src/crypto/signers/PlainDsaEncoding.cs b/crypto/src/crypto/signers/PlainDsaEncoding.cs
new file mode 100644
index 000000000..2e1f65a1f
--- /dev/null
+++ b/crypto/src/crypto/signers/PlainDsaEncoding.cs
@@ -0,0 +1,58 @@
+using System;
+
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Signers
+{
+    public class PlainDsaEncoding
+        : IDsaEncoding
+    {
+        public static readonly PlainDsaEncoding Instance = new PlainDsaEncoding();
+
+        public virtual BigInteger[] Decode(BigInteger n, byte[] encoding)
+        {
+            int valueLength = BigIntegers.GetUnsignedByteLength(n);
+            if (encoding.Length != valueLength * 2)
+                throw new ArgumentException("Encoding has incorrect length", "encoding");
+
+            return new BigInteger[] {
+                DecodeValue(n, encoding, 0, valueLength),
+                DecodeValue(n, encoding, valueLength, valueLength),
+            };
+        }
+
+        public virtual byte[] Encode(BigInteger n, BigInteger r, BigInteger s)
+        {
+            int valueLength = BigIntegers.GetUnsignedByteLength(n);
+            byte[] result = new byte[valueLength * 2];
+            EncodeValue(n, r, result, 0, valueLength);
+            EncodeValue(n, s, result, valueLength, valueLength);
+            return result;
+        }
+
+        protected virtual BigInteger CheckValue(BigInteger n, BigInteger x)
+        {
+            if (x.SignValue < 0 || x.CompareTo(n) >= 0)
+                throw new ArgumentException("Value out of range", "x");
+
+            return x;
+        }
+
+        protected virtual BigInteger DecodeValue(BigInteger n, byte[] buf, int off, int len)
+        {
+            return CheckValue(n, new BigInteger(1, buf, off, len));
+        }
+
+        protected virtual void EncodeValue(BigInteger n, BigInteger x, byte[] buf, int off, int len)
+        {
+            byte[] bs = CheckValue(n, x).ToByteArrayUnsigned();
+            int bsOff = System.Math.Max(0, bs.Length - len);
+            int bsLen = bs.Length - bsOff;
+
+            int pos = len - bsLen;
+            Arrays.Fill(buf, off, off + pos, 0);
+            Array.Copy(bs, bsOff, buf, off + pos, bsLen);
+        }
+    }
+}