1 files changed, 97 insertions, 0 deletions
diff --git a/bcprov/src/main/java/org/bouncycastle/crypto/prng/X931SecureRandomBuilder.java b/bcprov/src/main/java/org/bouncycastle/crypto/prng/X931SecureRandomBuilder.java
new file mode 100644
index 0000000..89c2905
--- /dev/null
+++ b/bcprov/src/main/java/org/bouncycastle/crypto/prng/X931SecureRandomBuilder.java
@@ -0,0 +1,97 @@
+package org.bouncycastle.crypto.prng;
+
+import java.security.SecureRandom;
+
+import org.bouncycastle.crypto.BlockCipher;
+import org.bouncycastle.crypto.params.KeyParameter;
+import org.bouncycastle.util.Pack;
+
+public class X931SecureRandomBuilder
+{
+    private SecureRandom random;          // JDK 1.1 complains on final.
+    private EntropySourceProvider entropySourceProvider;
+
+    private BlockCipher engine;
+    private byte[] dateTimeVector;
+
+    /**
+     * Basic constructor, creates a builder using an EntropySourceProvider based on the default SecureRandom with
+     * predictionResistant set to false.
+     * <p>
+     * Any SecureRandom created from a builder constructed like this will make use of input passed to SecureRandom.setSeed() if
+     * the default SecureRandom does for its generateSeed() call.
+     * </p>
+     */
+    public X931SecureRandomBuilder()
+    {
+        this(new SecureRandom(), false);
+    }
+
+    /**
+     * Construct a builder with an EntropySourceProvider based on the passed in SecureRandom and the passed in value
+     * for prediction resistance.
+     * <p>
+     * Any SecureRandom created from a builder constructed like this will make use of input passed to SecureRandom.setSeed() if
+     * the passed in SecureRandom does for its generateSeed() call.
+     * </p>
+     * @param entropySource
+     * @param predictionResistant
+     */
+    public X931SecureRandomBuilder(SecureRandom entropySource, boolean predictionResistant)
+    {
+        this.random = entropySource;
+        this.entropySourceProvider = new BasicEntropySourceProvider(random, predictionResistant);
+    }
+
+    /**
+     * Create a builder which makes creates the SecureRandom objects from a specified entropy source provider.
+     * <p>
+     * <b>Note:</b> If this constructor is used any calls to setSeed() in the resulting SecureRandom will be ignored.
+     * </p>
+     * @param entropySourceProvider a provider of EntropySource objects.
+     */
+    public X931SecureRandomBuilder(EntropySourceProvider entropySourceProvider)
+    {
+        this.random = null;
+        this.entropySourceProvider = entropySourceProvider;
+    }
+
+    public X931SecureRandomBuilder setDateTimeVector(byte[] dateTimeVector)
+    {
+        this.dateTimeVector = dateTimeVector;
+
+        return this;
+    }
+
+    /**
+     * Construct a X9.31 secure random generator using the passed in engine and key. If predictionResistant is true the
+     * generator will be reseeded on each request.
+     *
+     * @param engine a block cipher to use as the operator.
+     * @param key the block cipher key to initialise engine with.
+     * @param predictionResistant true if engine to be reseeded on each use, false otherwise.
+     * @return a SecureRandom.
+     */
+    public X931SecureRandom build(BlockCipher engine, KeyParameter key, boolean predictionResistant)
+    {
+        this.engine = engine;
+
+        if (dateTimeVector == null)
+        {
+            if (engine.getBlockSize() == 8)
+            {
+                dateTimeVector = Pack.longToBigEndian(System.currentTimeMillis());
+            }
+            else
+            {
+                dateTimeVector = new byte[engine.getBlockSize()];
+                byte[] date = Pack.longToBigEndian(System.currentTimeMillis());
+                System.arraycopy(date, 0, dateTimeVector, 0, date.length);
+            }
+        }
+
+        engine.init(true, key);
+
+        return new X931SecureRandom(random, new X931RNG(engine, dateTimeVector, entropySourceProvider.get(engine.getBlockSize() * 8)), predictionResistant);
+    }
+}