/*

 * Copyright (c) 1996, 2016, Oracle and/or its affiliates. All rights reserved.

 * 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.security.ssl;

import java.util.Map;

import java.util.HashMap;

import java.util.Collections;

import java.util.regex.Pattern;

import java.util.regex.Matcher;

import java.math.BigInteger;

import java.security.*;

import java.io.IOException;

import javax.net.ssl.SSLHandshakeException;

import javax.crypto.SecretKey;

import javax.crypto.KeyAgreement;

import javax.crypto.interfaces.DHPublicKey;

import javax.crypto.spec.*;

import java.util.EnumSet;

import sun.security.util.KeyUtil;

/**

 * This class implements the Diffie-Hellman key exchange algorithm.

 * D-H means combining your private key with your partners public key to

 * generate a number. The peer does the same with its private key and our

 * public key. Through the magic of Diffie-Hellman we both come up with the

 * same number. This number is secret (discounting MITM attacks) and hence

 * called the shared secret. It has the same length as the modulus, e.g. 512

 * or 1024 bit. Man-in-the-middle attacks are typically countered by an

 * independent authentication step using certificates (RSA, DSA, etc.).

 *

 * The thing to note is that the shared secret is constant for two partners

 * with constant private keys. This is often not what we want, which is why

 * it is generally a good idea to create a new private key for each session.

 * Generating a private key involves one modular exponentiation assuming

 * suitable D-H parameters are available.

 *

 * General usage of this class (TLS DHE case):

 *  . if we are server, call DHCrypt(keyLength,random). This generates

 *    an ephemeral keypair of the request length.

 *  . if we are client, call DHCrypt(modulus, base, random). This

 *    generates an ephemeral keypair using the parameters specified by

 *    the server.

 *  . send parameters and public value to remote peer

 *  . receive peers ephemeral public key

 *  . call getAgreedSecret() to calculate the shared secret

 *

 * In TLS the server chooses the parameter values itself, the client must use

 * those sent to it by the server.

 *

 * The use of ephemeral keys as described above also achieves what is called

 * "forward secrecy". This means that even if the authentication keys are

 * broken at a later date, the shared secret remains secure. The session is

 * compromised only if the authentication keys are already broken at the

 * time the key exchange takes place and an active MITM attack is used.

 * This is in contrast to straightforward encrypting RSA key exchanges.

 *

 * @author David Brownell

 */

final class DHCrypt {

    // group parameters (prime modulus and generator)

    private BigInteger modulus;                 // P (aka N)

    private BigInteger base;                    // G (aka alpha)

    // our private key (including private component x)

    private PrivateKey privateKey;

    // public component of our key, X = (g ^ x) mod p

    private BigInteger publicValue;             // X (aka y)

    // the times to recove from failure if public key validation

    private static int MAX_FAILOVER_TIMES = 2;

    /**

     * Generate a Diffie-Hellman keypair of the specified size.

     */

    DHCrypt(int keyLength, SecureRandom random) {

        this(keyLength,

                ParametersHolder.definedParams.get(keyLength), random);

    }

    /**

     * Generate a Diffie-Hellman keypair using the specified parameters.

     *

     * @param modulus the Diffie-Hellman modulus P

     * @param base the Diffie-Hellman base G

     */

    DHCrypt(BigInteger modulus, BigInteger base, SecureRandom random) {

        this(modulus.bitLength(),

                new DHParameterSpec(modulus, base), random);

    }

    /**

     * Generate a Diffie-Hellman keypair using the specified size and

     * parameters.

     */

    private DHCrypt(int keyLength,

            DHParameterSpec params, SecureRandom random) {

        try {

            KeyPairGenerator kpg = JsseJce.getKeyPairGenerator("DiffieHellman");

            if (params != null) {

                kpg.initialize(params, random);

            } else {

                kpg.initialize(keyLength, random);

            }

            DHPublicKeySpec spec = generateDHPublicKeySpec(kpg);

            if (spec == null) {

                throw new RuntimeException("Could not generate DH keypair");

            }

            publicValue = spec.getY();

            modulus = spec.getP();

            base = spec.getG();

        } catch (GeneralSecurityException e) {

            throw new RuntimeException("Could not generate DH keypair", e);

        }

    }

    static DHPublicKeySpec getDHPublicKeySpec(PublicKey key) {

        if (key instanceof DHPublicKey) {

            DHPublicKey dhKey = (DHPublicKey)key;

            DHParameterSpec params = dhKey.getParams();

            return new DHPublicKeySpec(dhKey.getY(),

                                    params.getP(), params.getG());

        }

        try {

            KeyFactory factory = JsseJce.getKeyFactory("DiffieHellman");

            return factory.getKeySpec(key, DHPublicKeySpec.class);

        } catch (Exception e) {

            throw new RuntimeException(e);

        }

    }

    /** Returns the Diffie-Hellman modulus. */

    BigInteger getModulus() {

        return modulus;

    }

    /** Returns the Diffie-Hellman base (generator).  */

    BigInteger getBase() {

        return base;

    }

    /**

     * Gets the public key of this end of the key exchange.

     */

    BigInteger getPublicKey() {

        return publicValue;

    }

    /**

     * Get the secret data that has been agreed on through Diffie-Hellman

     * key agreement protocol.  Note that in the two party protocol, if

     * the peer keys are already known, no other data needs to be sent in

     * order to agree on a secret.  That is, a secured message may be

     * sent without any mandatory round-trip overheads.

     *

     * <P>It is illegal to call this member function if the private key

     * has not been set (or generated).

     *

     * @param  peerPublicKey the peer's public key.

     * @param  keyIsValidated whether the {@code peerPublicKey} has beed

     *         validated

     * @return the secret, which is an unsigned big-endian integer

     *         the same size as the Diffie-Hellman modulus.

     */

    SecretKey getAgreedSecret(BigInteger peerPublicValue,

            boolean keyIsValidated) throws SSLHandshakeException {

        try {

            KeyFactory kf = JsseJce.getKeyFactory("DiffieHellman");

            DHPublicKeySpec spec =

                        new DHPublicKeySpec(peerPublicValue, modulus, base);

            PublicKey publicKey = kf.generatePublic(spec);

            KeyAgreement ka = JsseJce.getKeyAgreement("DiffieHellman");

            // validate the Diffie-Hellman public key

            if (!keyIsValidated &&

                    !KeyUtil.isOracleJCEProvider(ka.getProvider().getName())) {

                try {

                    KeyUtil.validate(spec);

                } catch (InvalidKeyException ike) {

                    // prefer handshake_failure alert to internal_error alert

                    throw new SSLHandshakeException(ike.getMessage());

                }

            }

            ka.init(privateKey);

            ka.doPhase(publicKey, true);

            return ka.generateSecret("TlsPremasterSecret");

        } catch (GeneralSecurityException e) {

            throw (SSLHandshakeException) new SSLHandshakeException(

                "Could not generate secret").initCause(e);

        }

    }

    // Check constraints of the specified DH public key.

    void checkConstraints(AlgorithmConstraints constraints,

            BigInteger peerPublicValue) throws SSLHandshakeException {

        try {

            KeyFactory kf = JsseJce.getKeyFactory("DiffieHellman");

            DHPublicKeySpec spec =

                        new DHPublicKeySpec(peerPublicValue, modulus, base);

            DHPublicKey publicKey = (DHPublicKey)kf.generatePublic(spec);

            // check constraints of DHPublicKey

            if (!constraints.permits(

                    EnumSet.of(CryptoPrimitive.KEY_AGREEMENT), publicKey)) {

                throw new SSLHandshakeException(

                    "DHPublicKey does not comply to algorithm constraints");

            }

        } catch (GeneralSecurityException gse) {

            throw (SSLHandshakeException) new SSLHandshakeException(

                    "Could not generate DHPublicKey").initCause(gse);

        }

    }

    // Generate and validate DHPublicKeySpec

    private DHPublicKeySpec generateDHPublicKeySpec(KeyPairGenerator kpg)

            throws GeneralSecurityException {

        boolean doExtraValiadtion =

                    (!KeyUtil.isOracleJCEProvider(kpg.getProvider().getName()));

        for (int i = 0; i <= MAX_FAILOVER_TIMES; i++) {

            KeyPair kp = kpg.generateKeyPair();

            privateKey = kp.getPrivate();

            DHPublicKeySpec spec = getDHPublicKeySpec(kp.getPublic());

            // validate the Diffie-Hellman public key

            if (doExtraValiadtion) {

                try {

                    KeyUtil.validate(spec);

                } catch (InvalidKeyException ivke) {

                    if (i == MAX_FAILOVER_TIMES) {

                        throw ivke;

                    }

                    // otherwise, ignore the exception and try the next one

                    continue;

                }

            }

            return spec;

        }

        return null;

    }

    // lazy initialization holder class idiom for static default parameters

    //

    // See Effective Java Second Edition: Item 71.

    private static class ParametersHolder {

        private final static boolean debugIsOn =

                (Debug.getInstance("ssl") != null) && Debug.isOn("sslctx");

        //

        // Default DH ephemeral parameters

        //

        private static final BigInteger p512 = new BigInteger(   // generated

                "D87780E15FF50B4ABBE89870188B049406B5BEA98AB23A02" +

                "41D88EA75B7755E669C08093D3F0CA7FC3A5A25CF067DCB9" +

                "A43DD89D1D90921C6328884461E0B6D3", 16);

        private static final BigInteger p768 = new BigInteger(   // RFC 2409

                "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" +

                "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" +

                "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" +

                "E485B576625E7EC6F44C42E9A63A3620FFFFFFFFFFFFFFFF", 16);

        private static final BigInteger p1024 = new BigInteger(  // RFC 2409

                "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" +

                "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" +

                "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" +

                "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" +

                "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381" +

                "FFFFFFFFFFFFFFFF", 16);

        private static final BigInteger p1536 = new BigInteger(  // RFC 3526

                "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" +

                "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" +

                "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" +

                "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" +

                "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3D" +

                "C2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F" +

                "83655D23DCA3AD961C62F356208552BB9ED529077096966D" +

                "670C354E4ABC9804F1746C08CA237327FFFFFFFFFFFFFFFF", 16);

        private static final BigInteger p2048 = new BigInteger(  // TLS FFDHE

                "FFFFFFFFFFFFFFFFADF85458A2BB4A9AAFDC5620273D3CF1" +

                "D8B9C583CE2D3695A9E13641146433FBCC939DCE249B3EF9" +

                "7D2FE363630C75D8F681B202AEC4617AD3DF1ED5D5FD6561" +

                "2433F51F5F066ED0856365553DED1AF3B557135E7F57C935" +

                "984F0C70E0E68B77E2A689DAF3EFE8721DF158A136ADE735" +

                "30ACCA4F483A797ABC0AB182B324FB61D108A94BB2C8E3FB" +

                "B96ADAB760D7F4681D4F42A3DE394DF4AE56EDE76372BB19" +

                "0B07A7C8EE0A6D709E02FCE1CDF7E2ECC03404CD28342F61" +

                "9172FE9CE98583FF8E4F1232EEF28183C3FE3B1B4C6FAD73" +

                "3BB5FCBC2EC22005C58EF1837D1683B2C6F34A26C1B2EFFA" +

                "886B423861285C97FFFFFFFFFFFFFFFF", 16);

        private static final BigInteger p3072 = new BigInteger(  // TLS FFDHE

                "FFFFFFFFFFFFFFFFADF85458A2BB4A9AAFDC5620273D3CF1" +

                "D8B9C583CE2D3695A9E13641146433FBCC939DCE249B3EF9" +

                "7D2FE363630C75D8F681B202AEC4617AD3DF1ED5D5FD6561" +

                "2433F51F5F066ED0856365553DED1AF3B557135E7F57C935" +

                "984F0C70E0E68B77E2A689DAF3EFE8721DF158A136ADE735" +

                "30ACCA4F483A797ABC0AB182B324FB61D108A94BB2C8E3FB" +

                "B96ADAB760D7F4681D4F42A3DE394DF4AE56EDE76372BB19" +

                "0B07A7C8EE0A6D709E02FCE1CDF7E2ECC03404CD28342F61" +

                "9172FE9CE98583FF8E4F1232EEF28183C3FE3B1B4C6FAD73" +

                "3BB5FCBC2EC22005C58EF1837D1683B2C6F34A26C1B2EFFA" +

                "886B4238611FCFDCDE355B3B6519035BBC34F4DEF99C0238" +

                "61B46FC9D6E6C9077AD91D2691F7F7EE598CB0FAC186D91C" +

                "AEFE130985139270B4130C93BC437944F4FD4452E2D74DD3" +

                "64F2E21E71F54BFF5CAE82AB9C9DF69EE86D2BC522363A0D" +

                "ABC521979B0DEADA1DBF9A42D5C4484E0ABCD06BFA53DDEF" +

                "3C1B20EE3FD59D7C25E41D2B66C62E37FFFFFFFFFFFFFFFF", 16);

        private static final BigInteger p4096 = new BigInteger(  // TLS FFDHE

                "FFFFFFFFFFFFFFFFADF85458A2BB4A9AAFDC5620273D3CF1" +

                "D8B9C583CE2D3695A9E13641146433FBCC939DCE249B3EF9" +

                "7D2FE363630C75D8F681B202AEC4617AD3DF1ED5D5FD6561" +

                "2433F51F5F066ED0856365553DED1AF3B557135E7F57C935" +

                "984F0C70E0E68B77E2A689DAF3EFE8721DF158A136ADE735" +

                "30ACCA4F483A797ABC0AB182B324FB61D108A94BB2C8E3FB" +

                "B96ADAB760D7F4681D4F42A3DE394DF4AE56EDE76372BB19" +

                "0B07A7C8EE0A6D709E02FCE1CDF7E2ECC03404CD28342F61" +

                "9172FE9CE98583FF8E4F1232EEF28183C3FE3B1B4C6FAD73" +

                "3BB5FCBC2EC22005C58EF1837D1683B2C6F34A26C1B2EFFA" +

                "886B4238611FCFDCDE355B3B6519035BBC34F4DEF99C0238" +

                "61B46FC9D6E6C9077AD91D2691F7F7EE598CB0FAC186D91C" +

                "AEFE130985139270B4130C93BC437944F4FD4452E2D74DD3" +

                "64F2E21E71F54BFF5CAE82AB9C9DF69EE86D2BC522363A0D" +

                "ABC521979B0DEADA1DBF9A42D5C4484E0ABCD06BFA53DDEF" +

                "3C1B20EE3FD59D7C25E41D2B669E1EF16E6F52C3164DF4FB" +

                "7930E9E4E58857B6AC7D5F42D69F6D187763CF1D55034004" +

                "87F55BA57E31CC7A7135C886EFB4318AED6A1E012D9E6832" +

                "A907600A918130C46DC778F971AD0038092999A333CB8B7A" +

                "1A1DB93D7140003C2A4ECEA9F98D0ACC0A8291CDCEC97DCF" +

                "8EC9B55A7F88A46B4DB5A851F44182E1C68A007E5E655F6A" +

                "FFFFFFFFFFFFFFFF", 16);

        private static final BigInteger p6144 = new BigInteger(  // TLS FFDHE

                "FFFFFFFFFFFFFFFFADF85458A2BB4A9AAFDC5620273D3CF1" +

                "D8B9C583CE2D3695A9E13641146433FBCC939DCE249B3EF9" +

                "7D2FE363630C75D8F681B202AEC4617AD3DF1ED5D5FD6561" +

                "2433F51F5F066ED0856365553DED1AF3B557135E7F57C935" +

                "984F0C70E0E68B77E2A689DAF3EFE8721DF158A136ADE735" +

                "30ACCA4F483A797ABC0AB182B324FB61D108A94BB2C8E3FB" +

                "B96ADAB760D7F4681D4F42A3DE394DF4AE56EDE76372BB19" +

                "0B07A7C8EE0A6D709E02FCE1CDF7E2ECC03404CD28342F61" +

                "9172FE9CE98583FF8E4F1232EEF28183C3FE3B1B4C6FAD73" +

                "3BB5FCBC2EC22005C58EF1837D1683B2C6F34A26C1B2EFFA" +

                "886B4238611FCFDCDE355B3B6519035BBC34F4DEF99C0238" +

                "61B46FC9D6E6C9077AD91D2691F7F7EE598CB0FAC186D91C" +

                "AEFE130985139270B4130C93BC437944F4FD4452E2D74DD3" +

                "64F2E21E71F54BFF5CAE82AB9C9DF69EE86D2BC522363A0D" +

                "ABC521979B0DEADA1DBF9A42D5C4484E0ABCD06BFA53DDEF" +

                "3C1B20EE3FD59D7C25E41D2B669E1EF16E6F52C3164DF4FB" +

                "7930E9E4E58857B6AC7D5F42D69F6D187763CF1D55034004" +

                "87F55BA57E31CC7A7135C886EFB4318AED6A1E012D9E6832" +

                "A907600A918130C46DC778F971AD0038092999A333CB8B7A" +

                "1A1DB93D7140003C2A4ECEA9F98D0ACC0A8291CDCEC97DCF" +

                "8EC9B55A7F88A46B4DB5A851F44182E1C68A007E5E0DD902" +

                "0BFD64B645036C7A4E677D2C38532A3A23BA4442CAF53EA6" +

                "3BB454329B7624C8917BDD64B1C0FD4CB38E8C334C701C3A" +

                "CDAD0657FCCFEC719B1F5C3E4E46041F388147FB4CFDB477" +

                "A52471F7A9A96910B855322EDB6340D8A00EF092350511E3" +

                "0ABEC1FFF9E3A26E7FB29F8C183023C3587E38DA0077D9B4" +

                "763E4E4B94B2BBC194C6651E77CAF992EEAAC0232A281BF6" +

                "B3A739C1226116820AE8DB5847A67CBEF9C9091B462D538C" +

                "D72B03746AE77F5E62292C311562A846505DC82DB854338A" +

                "E49F5235C95B91178CCF2DD5CACEF403EC9D1810C6272B04" +

                "5B3B71F9DC6B80D63FDD4A8E9ADB1E6962A69526D43161C1" +

                "A41D570D7938DAD4A40E329CD0E40E65FFFFFFFFFFFFFFFF", 16);

        private static final BigInteger p8192 = new BigInteger(  // TLS FFDHE

                "FFFFFFFFFFFFFFFFADF85458A2BB4A9AAFDC5620273D3CF1" +

                "D8B9C583CE2D3695A9E13641146433FBCC939DCE249B3EF9" +

                "7D2FE363630C75D8F681B202AEC4617AD3DF1ED5D5FD6561" +

                "2433F51F5F066ED0856365553DED1AF3B557135E7F57C935" +

                "984F0C70E0E68B77E2A689DAF3EFE8721DF158A136ADE735" +

                "30ACCA4F483A797ABC0AB182B324FB61D108A94BB2C8E3FB" +

                "B96ADAB760D7F4681D4F42A3DE394DF4AE56EDE76372BB19" +

                "0B07A7C8EE0A6D709E02FCE1CDF7E2ECC03404CD28342F61" +

                "9172FE9CE98583FF8E4F1232EEF28183C3FE3B1B4C6FAD73" +

                "3BB5FCBC2EC22005C58EF1837D1683B2C6F34A26C1B2EFFA" +

                "886B4238611FCFDCDE355B3B6519035BBC34F4DEF99C0238" +

                "61B46FC9D6E6C9077AD91D2691F7F7EE598CB0FAC186D91C" +

                "AEFE130985139270B4130C93BC437944F4FD4452E2D74DD3" +

                "64F2E21E71F54BFF5CAE82AB9C9DF69EE86D2BC522363A0D" +

                "ABC521979B0DEADA1DBF9A42D5C4484E0ABCD06BFA53DDEF" +

                "3C1B20EE3FD59D7C25E41D2B669E1EF16E6F52C3164DF4FB" +

                "7930E9E4E58857B6AC7D5F42D69F6D187763CF1D55034004" +

                "87F55BA57E31CC7A7135C886EFB4318AED6A1E012D9E6832" +

                "A907600A918130C46DC778F971AD0038092999A333CB8B7A" +

                "1A1DB93D7140003C2A4ECEA9F98D0ACC0A8291CDCEC97DCF" +

                "8EC9B55A7F88A46B4DB5A851F44182E1C68A007E5E0DD902" +

                "0BFD64B645036C7A4E677D2C38532A3A23BA4442CAF53EA6" +

                "3BB454329B7624C8917BDD64B1C0FD4CB38E8C334C701C3A" +

                "CDAD0657FCCFEC719B1F5C3E4E46041F388147FB4CFDB477" +

                "A52471F7A9A96910B855322EDB6340D8A00EF092350511E3" +

                "0ABEC1FFF9E3A26E7FB29F8C183023C3587E38DA0077D9B4" +

                "763E4E4B94B2BBC194C6651E77CAF992EEAAC0232A281BF6" +

                "B3A739C1226116820AE8DB5847A67CBEF9C9091B462D538C" +

                "D72B03746AE77F5E62292C311562A846505DC82DB854338A" +

                "E49F5235C95B91178CCF2DD5CACEF403EC9D1810C6272B04" +

                "5B3B71F9DC6B80D63FDD4A8E9ADB1E6962A69526D43161C1" +

                "A41D570D7938DAD4A40E329CCFF46AAA36AD004CF600C838" +

                "1E425A31D951AE64FDB23FCEC9509D43687FEB69EDD1CC5E" +

                "0B8CC3BDF64B10EF86B63142A3AB8829555B2F747C932665" +

                "CB2C0F1CC01BD70229388839D2AF05E454504AC78B758282" +

                "2846C0BA35C35F5C59160CC046FD8251541FC68C9C86B022" +

                "BB7099876A460E7451A8A93109703FEE1C217E6C3826E52C" +

                "51AA691E0E423CFC99E9E31650C1217B624816CDAD9A95F9" +

                "D5B8019488D9C0A0A1FE3075A577E23183F81D4A3F2FA457" +

                "1EFC8CE0BA8A4FE8B6855DFE72B0A66EDED2FBABFBE58A30" +

                "FAFABE1C5D71A87E2F741EF8C1FE86FEA6BBFDE530677F0D" +

                "97D11D49F7A8443D0822E506A9F4614E011E2A94838FF88C" +

                "D68C8BB7C5C6424CFFFFFFFFFFFFFFFF", 16);

        private static final BigInteger[] supportedPrimes = {

                p512, p768, p1024, p1536, p2048, p3072, p4096, p6144, p8192};

        // a measure of the uncertainty that prime modulus p is not a prime

        //

        // see BigInteger.isProbablePrime(int certainty)

        private final static int PRIME_CERTAINTY = 120;

        // the known security property, jdk.tls.server.defaultDHEParameters

        private final static String PROPERTY_NAME =

                "jdk.tls.server.defaultDHEParameters";

        private static final Pattern spacesPattern = Pattern.compile("\\s+");

        private final static Pattern syntaxPattern = Pattern.compile(

                "(\\{[0-9A-Fa-f]+,[0-9A-Fa-f]+\\})" +

                "(,\\{[0-9A-Fa-f]+,[0-9A-Fa-f]+\\})*");

        private static final Pattern paramsPattern = Pattern.compile(

                "\\{([0-9A-Fa-f]+),([0-9A-Fa-f]+)\\}");

        // cache of predefined default DH ephemeral parameters

        private final static Map<Integer,DHParameterSpec> definedParams;

        static {

            String property = AccessController.doPrivileged(

                new PrivilegedAction<String>() {

                    public String run() {

                        return Security.getProperty(PROPERTY_NAME);

                    }

                });

            if (property != null && !property.isEmpty()) {

                // remove double quote marks from beginning/end of the property

                if (property.length() >= 2 && property.charAt(0) == '"' &&

                        property.charAt(property.length() - 1) == '"') {

                    property = property.substring(1, property.length() - 1);

                }

                property = property.trim();

            }

            if (property != null && !property.isEmpty()) {

                Matcher spacesMatcher = spacesPattern.matcher(property);

                property = spacesMatcher.replaceAll("");

                if (debugIsOn) {

                    System.out.println("The Security Property " +

                            PROPERTY_NAME + ": " + property);

                }

            }

            Map<Integer,DHParameterSpec> defaultParams = new HashMap<>();

            if (property != null && !property.isEmpty()) {

                Matcher syntaxMatcher = syntaxPattern.matcher(property);

                if (syntaxMatcher.matches()) {

                    Matcher paramsFinder = paramsPattern.matcher(property);

                    while(paramsFinder.find()) {

                        String primeModulus = paramsFinder.group(1);

                        BigInteger p = new BigInteger(primeModulus, 16);