Initial revision

From-SVN: r102074
2005-07-16 00:30:23 +00:00
parent 6f4434b39b
commit f911ba985a
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+/* SHA1PRNG.java --- Secure Random SPI SHA1PRNG
+   Copyright (C) 1999, 2001, 2003, 2005 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+ 
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package gnu.java.security.provider;
+
+import java.io.Serializable;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandomSpi;
+import java.util.Random;
+
+public class SHA1PRNG extends SecureRandomSpi implements Serializable
+{
+  MessageDigest digest;
+  byte seed[];
+  byte data[];
+  int seedpos;
+  int datapos;
+  private boolean seeded = false; // set to true when we seed this
+  /**
+   * The size of seed.
+   */
+  private static final int SEED_SIZE = 20;
+  /**
+   * The size of data.
+   */
+  private static final int DATA_SIZE = 40;
+
+  /**
+   * Create a new SHA-1 pseudo-random number generator.
+   */
+  public SHA1PRNG()
+  {
+    try {
+      digest = MessageDigest.getInstance("SHA");
+    } catch ( NoSuchAlgorithmException nsae) {
+//      System.out.println("Failed to find SHA Message Digest: " + nsae);
+//      nsae.printStackTrace();
+      throw new InternalError ("no SHA implementation found");
+    }
+
+    seed = new byte[SEED_SIZE];
+    seedpos = 0;
+    data = new byte[DATA_SIZE];
+    datapos = SEED_SIZE;  // try to force hashing a first block
+  }
+
+  public void engineSetSeed(byte[] seed)
+  {
+    for(int i = 0; i < seed.length; i++)
+      this.seed[seedpos++ % SEED_SIZE] ^= seed[i];
+    seedpos %= SEED_SIZE;
+
+  }
+
+  public void engineNextBytes(byte[] bytes)
+  {
+    ensureIsSeeded ();
+    int loc = 0;
+    while (loc < bytes.length)
+      {
+	int copy = Math.min (bytes.length - loc, SEED_SIZE - datapos);
+
+	if (copy > 0)
+	  {
+	    System.arraycopy (data, datapos, bytes, loc, copy);
+	    datapos += copy;
+	    loc += copy;
+	  }
+	else
+	  {
+	    // No data ready for copying, so refill our buffer.
+	    System.arraycopy( seed, 0, data, SEED_SIZE, SEED_SIZE);
+	    byte[] digestdata = digest.digest( data );
+	    System.arraycopy( digestdata, 0, data, 0, SEED_SIZE);
+	    datapos = 0;
+	  }
+      }
+  }
+
+  public byte[] engineGenerateSeed(int numBytes)
+  {
+    byte tmp[] = new byte[numBytes];
+	
+    engineNextBytes( tmp );
+    return tmp;
+  }
+
+  private void ensureIsSeeded()
+  {
+    if (!seeded)
+      {
+        new Random(0L).nextBytes(seed);
+
+        byte[] digestdata = digest.digest(data);
+        System.arraycopy(digestdata, 0, data, 0, SEED_SIZE);
+
+        seeded = true;
+      }
+  }
+
+}