1 files changed, 74 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/generators/GOST3410KeyPairGenerator.java b/core/src/main/java/org/spongycastle/crypto/generators/GOST3410KeyPairGenerator.java
new file mode 100644
index 00000000..2929828b
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/generators/GOST3410KeyPairGenerator.java
@@ -0,0 +1,74 @@
+package org.spongycastle.crypto.generators;
+
+import org.spongycastle.crypto.AsymmetricCipherKeyPair;
+import org.spongycastle.crypto.AsymmetricCipherKeyPairGenerator;
+import org.spongycastle.crypto.KeyGenerationParameters;
+import org.spongycastle.crypto.params.GOST3410KeyGenerationParameters;
+import org.spongycastle.crypto.params.GOST3410Parameters;
+import org.spongycastle.crypto.params.GOST3410PrivateKeyParameters;
+import org.spongycastle.crypto.params.GOST3410PublicKeyParameters;
+import org.spongycastle.math.ec.WNafUtil;
+
+import java.math.BigInteger;
+import java.security.SecureRandom;
+
+/**
+ * a GOST3410 key pair generator.
+ * This generates GOST3410 keys in line with the method described
+ * in GOST R 34.10-94.
+ */
+public class GOST3410KeyPairGenerator
+        implements AsymmetricCipherKeyPairGenerator
+    {
+        private GOST3410KeyGenerationParameters param;
+
+        public void init(
+            KeyGenerationParameters param)
+        {
+            this.param = (GOST3410KeyGenerationParameters)param;
+        }
+
+        public AsymmetricCipherKeyPair generateKeyPair()
+        {
+            BigInteger      p, q, a, x, y;
+            GOST3410Parameters   GOST3410Params = param.getParameters();
+            SecureRandom    random = param.getRandom();
+
+            q = GOST3410Params.getQ();
+            p = GOST3410Params.getP();
+            a = GOST3410Params.getA();
+
+            int minWeight = 64;
+            for (;;)
+            {
+                x = new BigInteger(256, random);
+
+                if (x.signum() < 1 || x.compareTo(q) >= 0)
+                {
+                    continue;
+                }
+
+                /*
+                 * Require a minimum weight of the NAF representation, since low-weight primes may be
+                 * weak against a version of the number-field-sieve for the discrete-logarithm-problem.
+                 * 
+                 * See "The number field sieve for integers of low weight", Oliver Schirokauer.
+                 */
+                if (WNafUtil.getNafWeight(x) < minWeight)
+                {
+                    continue;
+                }
+
+                break;
+            }
+
+            //
+            // calculate the public key.
+            //
+            y = a.modPow(x, p);
+
+            return new AsymmetricCipherKeyPair(
+                    new GOST3410PublicKeyParameters(y, GOST3410Params),
+                    new GOST3410PrivateKeyParameters(x, GOST3410Params));
+        }
+    }