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1: /* SRPPublicKey.java -- 2: Copyright (C) 2003, 2006 Free Software Foundation, Inc. 3: 4: This file is a part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2 of the License, or (at 9: your option) any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; if not, write to the Free Software 18: Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 19: USA 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.javax.crypto.key.srp6; 40: 41: import gnu.java.security.Registry; 42: import gnu.java.security.key.IKeyPairCodec; 43: 44: import java.math.BigInteger; 45: import java.security.PublicKey; 46: 47: /** 48: * A representation of an SRP ephemeral public key. 49: * <p> 50: * Reference: 51: * <ol> 52: * <li><a href="http://srp.stanford.edu/design.html">SRP Protocol Design</a><br> 53: * Thomas J. Wu.</li> 54: * </ol> 55: */ 56: public class SRPPublicKey 57: extends SRPKey 58: implements PublicKey 59: { 60: /** 61: * The public exponent for either the server or the client engaged in the SRP 62: * protocol exchange. 63: */ 64: private final BigInteger Y; 65: 66: /** 67: * Public constructor for use from outside this package. 68: * 69: * @param N the public shared modulus. 70: * @param g the generator. 71: * @param Y the public exponent of the ephemeral key. 72: */ 73: public SRPPublicKey(BigInteger N, BigInteger g, BigInteger Y) 74: { 75: super(N, g); 76: 77: SRPAlgorithm.checkParams(N, g); 78: this.Y = Y; 79: } 80: 81: /** 82: * Default constructor. Assumes that N and g are already validated. 83: * 84: * @param params an array of 3 values representing N, g and Y; the latter 85: * being the client's or server's public exponent. 86: */ 87: SRPPublicKey(BigInteger[] params) 88: { 89: super(params[0], params[1]); 90: 91: this.Y = params[2]; 92: } 93: 94: /** 95: * A class method that takes the output of the <code>encodePublicKey()</code> 96: * method of an SRP keypair codec object (an instance implementing 97: * {@link IKeyPairCodec} for SRP keys, and re-constructs an instance of this 98: * object. 99: * 100: * @param k the contents of a previously encoded instance of this object. 101: * @throws ArrayIndexOutOfBoundsException if there is not enough bytes, in 102: * <code>k</code>, to represent a valid encoding of an instance 103: * of this object. 104: * @throws IllegalArgumentException if the byte sequence does not represent a 105: * valid encoding of an instance of this object. 106: */ 107: public static SRPPublicKey valueOf(byte[] k) 108: { 109: // check magic... 110: // we should parse here enough bytes to know which codec to use, and 111: // direct the byte array to the appropriate codec. since we only have one 112: // codec, we could have immediately tried it; nevertheless since testing 113: // one byte is cheaper than instatiating a codec that will fail we test 114: // the first byte before we carry on. 115: if (k[0] == Registry.MAGIC_RAW_SRP_PUBLIC_KEY[0]) 116: { 117: // it's likely to be in raw format. get a raw codec and hand it over 118: IKeyPairCodec codec = new SRPKeyPairRawCodec(); 119: return (SRPPublicKey) codec.decodePublicKey(k); 120: } 121: throw new IllegalArgumentException("magic"); 122: } 123: 124: /** 125: * Returns the public exponent of the key as a {@link BigInteger}. 126: * 127: * @return the public exponent of the key as a {@link BigInteger}. 128: */ 129: public BigInteger getY() 130: { 131: return Y; 132: } 133: 134: /** 135: * Returns the encoded form of this public key according to the designated 136: * format. 137: * 138: * @param format the desired format identifier of the resulting encoding. 139: * @return the byte sequence encoding this key according to the designated 140: * format. 141: * @throws IllegalArgumentException if the format is not supported. 142: */ 143: public byte[] getEncoded(int format) 144: { 145: byte[] result; 146: switch (format) 147: { 148: case IKeyPairCodec.RAW_FORMAT: 149: result = new SRPKeyPairRawCodec().encodePublicKey(this); 150: break; 151: default: 152: throw new IllegalArgumentException("format"); 153: } 154: return result; 155: } 156: 157: /** 158: * Returns <code>true</code> if the designated object is an instance of 159: * <code>SRPPublicKey</code>and has the same SRP parameter values as this 160: * one. 161: * 162: * @param obj the other non-null SRP key to compare to. 163: * @return <code>true</code> if the designated object is of the same type 164: * and value as this one. 165: */ 166: public boolean equals(Object obj) 167: { 168: if (obj == null) 169: return false; 170: if (! (obj instanceof SRPPublicKey)) 171: return false; 172: SRPPublicKey that = (SRPPublicKey) obj; 173: return super.equals(that) && Y.equals(that.getY()); 174: } 175: }