1 files changed, 72 insertions, 0 deletions
diff --git a/crypto/src/util/BigIntegers.cs b/crypto/src/util/BigIntegers.cs
new file mode 100644
index 000000000..df82e1f22
--- /dev/null
+++ b/crypto/src/util/BigIntegers.cs
@@ -0,0 +1,72 @@
+using System;
+
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Security;
+
+namespace Org.BouncyCastle.Utilities
+{
+	/**
+	 * BigInteger utilities.
+	 */
+	public sealed class BigIntegers
+	{
+		private const int MaxIterations = 1000;
+
+		private BigIntegers()
+		{
+		}
+
+		/**
+		* Return the passed in value as an unsigned byte array.
+		*
+		* @param value value to be converted.
+		* @return a byte array without a leading zero byte if present in the signed encoding.
+		*/
+		public static byte[] AsUnsignedByteArray(
+			BigInteger n)
+		{
+			return n.ToByteArrayUnsigned();
+		}
+
+		/**
+		* Return a random BigInteger not less than 'min' and not greater than 'max'
+		* 
+		* @param min the least value that may be generated
+		* @param max the greatest value that may be generated
+		* @param random the source of randomness
+		* @return a random BigInteger value in the range [min,max]
+		*/
+		public static BigInteger CreateRandomInRange(
+			BigInteger		min,
+			BigInteger		max,
+			// TODO Should have been just Random class
+			SecureRandom	random)
+		{
+			int cmp = min.CompareTo(max);
+			if (cmp >= 0)
+			{
+				if (cmp > 0)
+					throw new ArgumentException("'min' may not be greater than 'max'");
+
+				return min;
+			}
+
+			if (min.BitLength > max.BitLength / 2)
+			{
+				return CreateRandomInRange(BigInteger.Zero, max.Subtract(min), random).Add(min);
+			}
+
+			for (int i = 0; i < MaxIterations; ++i)
+			{
+				BigInteger x = new BigInteger(max.BitLength, random);
+				if (x.CompareTo(min) >= 0 && x.CompareTo(max) <= 0)
+				{
+					return x;
+				}
+			}
+
+			// fall back to a faster (restricted) method
+			return new BigInteger(max.Subtract(min).BitLength - 1, random).Add(min);
+		}
+	}
+}