| /* SRPKeyPairGenerator.java -- |
| Copyright (C) 2003, 2006 Free Software Foundation, Inc. |
| |
| This file is a 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 of the License, 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; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin St, 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.javax.crypto.key.srp6; |
| |
| import gnu.java.security.Configuration; |
| import gnu.java.security.Registry; |
| import gnu.java.security.key.IKeyPairGenerator; |
| import gnu.java.security.util.PRNG; |
| |
| import java.math.BigInteger; |
| import java.security.KeyPair; |
| import java.security.SecureRandom; |
| import java.util.Map; |
| import java.util.logging.Logger; |
| |
| /** |
| * Reference: |
| * <ol> |
| * <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br> |
| * Thomas J. Wu.</li> |
| * </ol> |
| */ |
| public class SRPKeyPairGenerator |
| implements IKeyPairGenerator |
| { |
| private static final Logger log = Logger.getLogger(SRPKeyPairGenerator.class.getName()); |
| private static final BigInteger ZERO = BigInteger.ZERO; |
| private static final BigInteger ONE = BigInteger.ONE; |
| private static final BigInteger TWO = BigInteger.valueOf(2L); |
| private static final BigInteger THREE = BigInteger.valueOf(3L); |
| /** Property name of the length (Integer) of the modulus (N) of an SRP key. */ |
| public static final String MODULUS_LENGTH = "gnu.crypto.srp.L"; |
| /** Property name of the Boolean indicating wether or not to use defaults. */ |
| public static final String USE_DEFAULTS = "gnu.crypto.srp.use.defaults"; |
| /** Property name of the modulus (N) of an SRP key. */ |
| public static final String SHARED_MODULUS = "gnu.crypto.srp.N"; |
| /** Property name of the generator (g) of an SRP key. */ |
| public static final String GENERATOR = "gnu.crypto.srp.g"; |
| /** Property name of the user's verifier (v) for a Server SRP key. */ |
| public static final String USER_VERIFIER = "gnu.crypto.srp.v"; |
| /** |
| * Property name of an optional {@link SecureRandom} instance to use. The |
| * default is to use a classloader singleton from {@link PRNG}. |
| */ |
| public static final String SOURCE_OF_RANDOMNESS = "gnu.crypto.srp.prng"; |
| /** Default value for the modulus length. */ |
| private static final int DEFAULT_MODULUS_LENGTH = 1024; |
| /** The optional {@link SecureRandom} instance to use. */ |
| private SecureRandom rnd = null; |
| /** Bit length of the shared modulus. */ |
| private int l; |
| /** The shared public modulus. */ |
| private BigInteger N; |
| /** The Field generator. */ |
| private BigInteger g; |
| /** The user's verifier MPI. */ |
| private BigInteger v; |
| /** Our default source of randomness. */ |
| private PRNG prng = null; |
| |
| // implicit 0-arguments constructor |
| |
| public String name() |
| { |
| return Registry.SRP_KPG; |
| } |
| |
| public void setup(Map attributes) |
| { |
| // do we have a SecureRandom, or should we use our own? |
| rnd = (SecureRandom) attributes.get(SOURCE_OF_RANDOMNESS); |
| N = (BigInteger) attributes.get(SHARED_MODULUS); |
| if (N != null) |
| { |
| l = N.bitLength(); |
| g = (BigInteger) attributes.get(GENERATOR); |
| if (g == null) |
| g = TWO; |
| SRPAlgorithm.checkParams(N, g); |
| } |
| else |
| { // generate or use default values for N and g |
| Boolean useDefaults = (Boolean) attributes.get(USE_DEFAULTS); |
| if (useDefaults == null) |
| useDefaults = Boolean.TRUE; |
| Integer L = (Integer) attributes.get(MODULUS_LENGTH); |
| l = DEFAULT_MODULUS_LENGTH; |
| if (useDefaults.equals(Boolean.TRUE)) |
| { |
| if (L != null) |
| { |
| l = L.intValue(); |
| switch (l) |
| { |
| case 512: |
| N = SRPAlgorithm.N_512; |
| break; |
| case 640: |
| N = SRPAlgorithm.N_640; |
| break; |
| case 768: |
| N = SRPAlgorithm.N_768; |
| break; |
| case 1024: |
| N = SRPAlgorithm.N_1024; |
| break; |
| case 1280: |
| N = SRPAlgorithm.N_1280; |
| break; |
| case 1536: |
| N = SRPAlgorithm.N_1536; |
| break; |
| case 2048: |
| N = SRPAlgorithm.N_2048; |
| break; |
| default: |
| throw new IllegalArgumentException( |
| "unknown default shared modulus bit length"); |
| } |
| g = TWO; |
| l = N.bitLength(); |
| } |
| } |
| else // generate new N and g |
| { |
| if (L != null) |
| { |
| l = L.intValue(); |
| if ((l % 256) != 0 || l < 512 || l > 2048) |
| throw new IllegalArgumentException( |
| "invalid shared modulus bit length"); |
| } |
| } |
| } |
| // are we using this generator on the server side, or the client side? |
| v = (BigInteger) attributes.get(USER_VERIFIER); |
| } |
| |
| public KeyPair generate() |
| { |
| if (N == null) |
| { |
| BigInteger[] params = generateParameters(); |
| BigInteger q = params[0]; |
| N = params[1]; |
| g = params[2]; |
| if (Configuration.DEBUG) |
| { |
| log.fine("q: " + q.toString(16)); |
| log.fine("N: " + N.toString(16)); |
| log.fine("g: " + g.toString(16)); |
| } |
| } |
| return (v != null ? hostKeyPair() : userKeyPair()); |
| } |
| |
| private synchronized BigInteger[] generateParameters() |
| { |
| // N A large safe prime (N = 2q+1, where q is prime) |
| // g A generator modulo N |
| BigInteger q, p, g; |
| byte[] qBytes = new byte[l / 8]; |
| do |
| { |
| do |
| { |
| nextRandomBytes(qBytes); |
| q = new BigInteger(1, qBytes); |
| q = q.setBit(0).setBit(l - 2).clearBit(l - 1); |
| } |
| while (! q.isProbablePrime(80)); |
| p = q.multiply(TWO).add(ONE); |
| } |
| while (p.bitLength() != l || ! p.isProbablePrime(80)); |
| // compute g. from FIPS-186, Appendix 4: e == 2 |
| BigInteger p_minus_1 = p.subtract(ONE); |
| g = TWO; |
| // Set h = any integer, where 1 < h < p - 1 and |
| // h differs from any value previously tried |
| for (BigInteger h = TWO; h.compareTo(p_minus_1) < 0; h = h.add(ONE)) |
| { |
| // Set g = h**2 mod p |
| g = h.modPow(TWO, p); |
| // If g = 1, go to step 3 |
| if (! g.equals(ONE)) |
| break; |
| } |
| return new BigInteger[] { q, p, g }; |
| } |
| |
| private KeyPair hostKeyPair() |
| { |
| byte[] bBytes = new byte[(l + 7) / 8]; |
| BigInteger b, B; |
| do |
| { |
| do |
| { |
| nextRandomBytes(bBytes); |
| b = new BigInteger(1, bBytes); |
| } |
| while (b.compareTo(ONE) <= 0 || b.compareTo(N) >= 0); |
| B = THREE.multiply(v).add(g.modPow(b, N)).mod(N); |
| } |
| while (B.compareTo(ZERO) == 0 || B.compareTo(N) >= 0); |
| KeyPair result = new KeyPair(new SRPPublicKey(new BigInteger[] { N, g, B }), |
| new SRPPrivateKey(new BigInteger[] { N, g, b, v })); |
| return result; |
| } |
| |
| private KeyPair userKeyPair() |
| { |
| byte[] aBytes = new byte[(l + 7) / 8]; |
| BigInteger a, A; |
| do |
| { |
| do |
| { |
| nextRandomBytes(aBytes); |
| a = new BigInteger(1, aBytes); |
| } |
| while (a.compareTo(ONE) <= 0 || a.compareTo(N) >= 0); |
| A = g.modPow(a, N); |
| } |
| while (A.compareTo(ZERO) == 0 || A.compareTo(N) >= 0); |
| KeyPair result = new KeyPair(new SRPPublicKey(new BigInteger[] { N, g, A }), |
| new SRPPrivateKey(new BigInteger[] { N, g, a })); |
| return result; |
| } |
| |
| private void nextRandomBytes(byte[] buffer) |
| { |
| if (rnd != null) |
| rnd.nextBytes(buffer); |
| else |
| getDefaultPRNG().nextBytes(buffer); |
| } |
| |
| private PRNG getDefaultPRNG() |
| { |
| if (prng == null) |
| prng = PRNG.getInstance(); |
| |
| return prng; |
| } |
| } |