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+/* DSASignature.java --
+ Copyright (C) 1999, 2003, 2004 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 gnu.java.security.der.DER;
+import gnu.java.security.der.DERReader;
+import gnu.java.security.der.DERValue;
+import gnu.java.security.der.DERWriter;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.math.BigInteger;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.InvalidParameterException;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.PrivateKey;
+import java.security.PublicKey;
+import java.security.SecureRandom;
+import java.security.SignatureException;
+import java.security.SignatureSpi;
+import java.security.interfaces.DSAPrivateKey;
+import java.security.interfaces.DSAPublicKey;
+import java.security.spec.AlgorithmParameterSpec;
+import java.util.ArrayList;
+import java.util.Random;
+
+public class DSASignature extends SignatureSpi
+{
+ private DSAPublicKey publicKey;
+ private DSAPrivateKey privateKey;
+ private final MessageDigest digest;
+ private final SecureRandom random;
+
+ public DSASignature() throws NoSuchAlgorithmException
+ {
+ random = new SecureRandom();
+ digest = MessageDigest.getInstance ("SHA1");
+ }
+
+ private void init()
+ {
+ digest.reset();
+ }
+
+ public void engineInitVerify (PublicKey publicKey)
+ throws InvalidKeyException
+ {
+ if (publicKey instanceof DSAPublicKey)
+ this.publicKey = (DSAPublicKey) publicKey;
+ else
+ throw new InvalidKeyException();
+ init();
+ }
+
+ public void engineInitSign (PrivateKey privateKey)
+ throws InvalidKeyException
+ {
+ if (privateKey instanceof DSAPrivateKey)
+ this.privateKey = (DSAPrivateKey) privateKey;
+ else
+ throw new InvalidKeyException ("not a DSA private key");
+
+ init();
+ }
+
+ public void engineInitSign (PrivateKey privateKey,
+ SecureRandom random)
+ throws InvalidKeyException
+ {
+ if (privateKey instanceof DSAPrivateKey)
+ this.privateKey = (DSAPrivateKey) privateKey;
+ else
+ throw new InvalidKeyException ("not a DSA private key");
+
+ appRandom = random;
+ init();
+ }
+
+ public void engineUpdate(byte b)
+ throws SignatureException
+ {
+ digest.update (b);
+ }
+
+ public void engineUpdate (byte[] b, int off, int len)
+ throws SignatureException
+ {
+ digest.update (b, off, len);
+ }
+
+ public byte[] engineSign() throws SignatureException
+ {
+ if (privateKey == null)
+ throw new SignatureException ("not initialized for signing");
+
+ try
+ {
+ BigInteger g = privateKey.getParams().getG();
+ BigInteger p = privateKey.getParams().getP();
+ BigInteger q = privateKey.getParams().getQ();
+
+ BigInteger x = privateKey.getX();
+
+ BigInteger k = new BigInteger (159, appRandom != null ? appRandom : random);
+
+ BigInteger r = g.modPow(k, p);
+ r = r.mod(q);
+
+ byte bytes[] = digest.digest();
+ BigInteger sha = new BigInteger (1, bytes);
+
+ BigInteger s = sha.add (x.multiply (r));
+ s = s.multiply (k.modInverse(q)).mod (q);
+
+ ByteArrayOutputStream bout = new ByteArrayOutputStream();
+ ArrayList seq = new ArrayList (2);
+ seq.add(0, new DERValue (DER.INTEGER, r));
+ seq.add(1, new DERValue (DER.INTEGER, s));
+ DERWriter.write (bout, new DERValue (DER.CONSTRUCTED | DER.SEQUENCE, seq));
+ return bout.toByteArray();
+ }
+ catch (IOException ioe)
+ {
+ SignatureException se = new SignatureException();
+ se.initCause (ioe);
+ throw se;
+ }
+ catch (ArithmeticException ae)
+ {
+ SignatureException se = new SignatureException();
+ se.initCause (ae);
+ throw se;
+ }
+ }
+
+ public int engineSign (byte[] outbuf, int offset, int len)
+ throws SignatureException
+ {
+ byte tmp[] = engineSign();
+ if (tmp.length > len)
+ throw new SignatureException ("output buffer too short");
+ System.arraycopy (tmp, 0, outbuf, offset, tmp.length);
+ return tmp.length;
+ }
+
+ public boolean engineVerify (byte[] sigBytes)
+ throws SignatureException
+ {
+ // Decode sigBytes from ASN.1 DER encoding
+ try
+ {
+ DERReader in = new DERReader (sigBytes);
+ DERValue val = in.read();
+ if (!val.isConstructed())
+ throw new SignatureException ("badly formed signature");
+ BigInteger r = (BigInteger) in.read().getValue();
+ BigInteger s = (BigInteger) in.read().getValue();
+
+ BigInteger g = publicKey.getParams().getG();
+ BigInteger p = publicKey.getParams().getP();
+ BigInteger q = publicKey.getParams().getQ();
+
+ BigInteger y = publicKey.getY();
+
+ BigInteger w = s.modInverse (q);
+
+ byte bytes[] = digest.digest();
+ BigInteger sha = new BigInteger (1, bytes);
+
+ BigInteger u1 = w.multiply (sha).mod ( q );
+
+ BigInteger u2 = r.multiply (w).mod(q);
+
+ BigInteger v = g.modPow (u1, p).multiply (y.modPow (u2, p)).mod (p).mod (q);
+
+ if (v.equals (r))
+ return true;
+ else
+ return false;
+ }
+ catch (IOException ioe)
+ {
+ SignatureException se = new SignatureException ("badly formed signature");
+ se.initCause (ioe);
+ throw se;
+ }
+ }
+
+ public void engineSetParameter (String param,
+ Object value)
+ throws InvalidParameterException
+ {
+ throw new InvalidParameterException();
+ }
+
+ public void engineSetParameter (AlgorithmParameterSpec params)
+ throws InvalidAlgorithmParameterException
+ {
+ throw new InvalidParameterException();
+
+ }
+
+ public Object engineGetParameter (String param)
+ throws InvalidParameterException
+ {
+ throw new InvalidParameterException();
+ }
+
+ public Object clone() throws CloneNotSupportedException
+ {
+ return super.clone();
+ }
+}
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