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
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+++ 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);
+ }
+ }
+}
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