1 files changed, 53 insertions, 0 deletions
diff --git a/Crypto/src/crypto/generators/DHKeyGeneratorHelper.cs b/Crypto/src/crypto/generators/DHKeyGeneratorHelper.cs
new file mode 100644
index 000000000..756e8482a
--- /dev/null
+++ b/Crypto/src/crypto/generators/DHKeyGeneratorHelper.cs
@@ -0,0 +1,53 @@
+using System;
+
+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Security;
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Generators
+{
+ class DHKeyGeneratorHelper
+ {
+ internal static readonly DHKeyGeneratorHelper Instance = new DHKeyGeneratorHelper();
+
+ private DHKeyGeneratorHelper()
+ {
+ }
+
+ internal BigInteger CalculatePrivate(
+ DHParameters dhParams,
+ SecureRandom random)
+ {
+ int limit = dhParams.L;
+
+ if (limit != 0)
+ {
+ return new BigInteger(limit, random).SetBit(limit - 1);
+ }
+
+ BigInteger min = BigInteger.Two;
+ int m = dhParams.M;
+ if (m != 0)
+ {
+ min = BigInteger.One.ShiftLeft(m - 1);
+ }
+
+ BigInteger max = dhParams.P.Subtract(BigInteger.Two);
+ BigInteger q = dhParams.Q;
+ if (q != null)
+ {
+ max = q.Subtract(BigInteger.Two);
+ }
+
+ return BigIntegers.CreateRandomInRange(min, max, random);
+ }
+
+ internal BigInteger CalculatePublic(
+ DHParameters dhParams,
+ BigInteger x)
+ {
+ return dhParams.G.ModPow(x, dhParams.P);
+ }
+ }
+}
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