1 files changed, 40 insertions, 0 deletions
diff --git a/Crypto/src/crypto/modes/gcm/BasicGcmExponentiator.cs b/Crypto/src/crypto/modes/gcm/BasicGcmExponentiator.cs
new file mode 100644
index 000000000..98049e1db
--- /dev/null
+++ b/Crypto/src/crypto/modes/gcm/BasicGcmExponentiator.cs
@@ -0,0 +1,40 @@
+using System;
+
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Modes.Gcm
+{
+ public class BasicGcmExponentiator
+ : IGcmExponentiator
+ {
+ private byte[] x;
+
+ public void Init(byte[] x)
+ {
+ this.x = Arrays.Clone(x);
+ }
+
+ public void ExponentiateX(long pow, byte[] output)
+ {
+ // Initial value is little-endian 1
+ byte[] y = GcmUtilities.OneAsBytes();
+
+ if (pow > 0)
+ {
+ byte[] powX = Arrays.Clone(x);
+ do
+ {
+ if ((pow & 1L) != 0)
+ {
+ GcmUtilities.Multiply(y, powX);
+ }
+ GcmUtilities.Multiply(powX, powX);
+ pow >>= 1;
+ }
+ while (pow > 0);
+ }
+
+ Array.Copy(y, 0, output, 0, 16);
+ }
+ }
+}
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