/*

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

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 */

/*

 * @test

 * @summary verify that modPow() not broken by the special case for 65537 (use -Dseed=X to set PRNG seed)

 * @author Andreas Sterbenz

 * @key randomness

 */

import java.math.BigInteger;

import java.security.*;

import java.security.spec.*;

public class ModPow65537 {

    public static void main(String[] args) throws Exception {

        // SunRsaSign uses BigInteger internally

        KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA", "SunRsaSign");

        kpg.initialize(new RSAKeyGenParameterSpec(512, BigInteger.valueOf(65537)));

        KeyPair kp = kpg.generateKeyPair();

        testSigning(kp);

        kpg.initialize(new RSAKeyGenParameterSpec(512, BigInteger.valueOf(65539)));

        kp = kpg.generateKeyPair();

        testSigning(kp);

        kpg.initialize(new RSAKeyGenParameterSpec(512, BigInteger.valueOf(3)));

        kp = kpg.generateKeyPair();

        testSigning(kp);

        // basic known answer test

        BigInteger base = new BigInteger("19058071224156864789844466979330892664777520457048234786139035643344145635582");

        BigInteger mod  = new BigInteger("75554098474976067521257305210610421240510163914613117319380559667371251381587");

        BigInteger exp1 = BigInteger.valueOf(65537);

        BigInteger exp2 = BigInteger.valueOf(75537);

        BigInteger exp3 = new BigInteger("13456870775607312149");

        BigInteger res1 = new BigInteger("5770048609366563851320890693196148833634112303472168971638730461010114147506");

        BigInteger res2 = new BigInteger("63446979364051087123350579021875958137036620431381329472348116892915461751531");

        BigInteger res3 = new BigInteger("39016891919893878823999350081191675846357272199067075794096200770872982089502");

        if (base.modPow(exp1, mod).equals(res1) == false) {

            throw new Exception("Error using " + exp1);

        }

        if (base.modPow(exp2, mod).equals(res2) == false) {

            throw new Exception("Error using " + exp2);

        }

        if (base.modPow(exp3, mod).equals(res3) == false) {

            throw new Exception("Error using " + exp3);

        }

        System.out.println("Passed");

    }

    private static void testSigning(KeyPair kp) throws Exception {

        System.out.println(kp.getPublic());

        byte[] data = new byte[1024];

        Signature sig = Signature.getInstance("SHA1withRSA", "SunRsaSign");

        sig.initSign(kp.getPrivate());

        sig.update(data);

        byte[] sigBytes = sig.sign();

        sig.initVerify(kp.getPublic());

        sig.update(data);

        if (sig.verify(sigBytes) == false) {

            throw new Exception("signature verification failed");

        }

        System.out.println("OK");

    }

}