1 files changed, 147 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/prng/FixedSecureRandom.java b/core/src/main/java/org/spongycastle/crypto/prng/FixedSecureRandom.java
new file mode 100644
index 00000000..cea20329
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/crypto/prng/FixedSecureRandom.java
@@ -0,0 +1,147 @@
+package org.spongycastle.crypto.prng;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.security.SecureRandom;
+
+/**
+ * A secure random that returns pre-seeded data to calls of nextBytes() or generateSeed().
+ */
+public class FixedSecureRandom
+    extends SecureRandom
+{
+    private byte[]       _data;
+    
+    private int          _index;
+    private int          _intPad;
+    
+    public FixedSecureRandom(byte[] value)
+    {
+        this(false, new byte[][] { value });
+    }
+    
+    public FixedSecureRandom(
+        byte[][] values)
+    {
+        this(false, values);
+    }
+    
+    /**
+     * Pad the data on integer boundaries. This is necessary for the classpath project's BigInteger
+     * implementation.
+     */
+    public FixedSecureRandom(
+        boolean intPad,
+        byte[] value)
+    {
+        this(intPad, new byte[][] { value });
+    }
+    
+    /**
+     * Pad the data on integer boundaries. This is necessary for the classpath project's BigInteger
+     * implementation.
+     */
+    public FixedSecureRandom(
+        boolean intPad,
+        byte[][] values)
+    {
+        ByteArrayOutputStream bOut = new ByteArrayOutputStream();
+        
+        for (int i = 0; i != values.length; i++)
+        {
+            try
+            {
+                bOut.write(values[i]);
+            }
+            catch (IOException e)
+            {
+                throw new IllegalArgumentException("can't save value array.");
+            }
+        }
+        
+        _data = bOut.toByteArray();
+        
+        if (intPad)
+        {
+            _intPad = _data.length % 4;
+        }
+    }
+
+    public void nextBytes(byte[] bytes)
+    {
+        System.arraycopy(_data, _index, bytes, 0, bytes.length);
+        
+        _index += bytes.length;
+    }
+
+    public byte[] generateSeed(int numBytes)
+    {
+        byte[] bytes = new byte[numBytes];
+
+        this.nextBytes(bytes);
+
+        return bytes;
+    }
+
+    //
+    // classpath's implementation of SecureRandom doesn't currently go back to nextBytes
+    // when next is called. We can't override next as it's a final method.
+    //
+    public int nextInt()
+    {
+        int val = 0;
+        
+        val |= nextValue() << 24;
+        val |= nextValue() << 16;
+        
+        if (_intPad == 2)
+        {
+            _intPad--;
+        }
+        else
+        {
+            val |= nextValue() << 8;
+        }
+        
+        if (_intPad == 1)
+        {
+            _intPad--;
+        }
+        else
+        {
+            val |= nextValue();
+        }
+        
+        return val;
+    }
+    
+    //
+    // classpath's implementation of SecureRandom doesn't currently go back to nextBytes
+    // when next is called. We can't override next as it's a final method.
+    //
+    public long nextLong()
+    {
+        long val = 0;
+        
+        val |= (long)nextValue() << 56;
+        val |= (long)nextValue() << 48;
+        val |= (long)nextValue() << 40;
+        val |= (long)nextValue() << 32;
+        val |= (long)nextValue() << 24;
+        val |= (long)nextValue() << 16;
+        val |= (long)nextValue() << 8;
+        val |= (long)nextValue();
+        
+        return val;
+    }
+
+    public boolean isExhausted()
+    {
+        return _index == _data.length;
+    }
+
+    private int nextValue()
+    {
+        return _data[_index++] & 0xff;
+    }
+}