1 files changed, 36 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/gcm/BasicGCMExponentiator.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/gcm/BasicGCMExponentiator.java
new file mode 100644
index 000000000..b84fe6f0f
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/gcm/BasicGCMExponentiator.java
@@ -0,0 +1,36 @@
+package org.spongycastle.crypto.modes.gcm;
+
+import org.spongycastle.util.Arrays;
+
+public class BasicGCMExponentiator implements GCMExponentiator
+{
+    private int[] x;
+
+    public void init(byte[] x)
+    {
+        this.x = GCMUtil.asInts(x);
+    }
+
+    public void exponentiateX(long pow, byte[] output)
+    {
+        // Initial value is little-endian 1
+        int[] y = GCMUtil.oneAsInts();
+
+        if (pow > 0)
+        {
+            int[] powX = Arrays.clone(x);
+            do
+            {
+                if ((pow & 1L) != 0)
+                {
+                    GCMUtil.multiply(y, powX);
+                }
+                GCMUtil.multiply(powX, powX);
+                pow >>>= 1;
+            }
+            while (pow > 0);
+        }
+
+        GCMUtil.asBytes(y, output);
+    }
+}