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1: /* SRPPrivateKey.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.PrivateKey; 46: 47: /** 48: * A representation of an SRP ephemeral private 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 SRPPrivateKey 57: extends SRPKey 58: implements PrivateKey 59: { 60: /** 61: * The private exponent for either the server or the client engaged in the SRP 62: * protocol exchange. 63: */ 64: private final BigInteger X; 65: /** 66: * The user's verifier (v) --for the server-- also computed at the client side 67: * as g.modPow(x, N), where x is the hashed output of the user name and 68: * password . 69: */ 70: private final BigInteger v; 71: 72: /** 73: * Public constructor for use from outside this package. 74: * 75: * @param N the public shared modulus. 76: * @param g the generator. 77: * @param x the private exponent of the ephemeral key. 78: */ 79: public SRPPrivateKey(BigInteger N, BigInteger g, BigInteger x) 80: { 81: this(N, g, x, null); 82: } 83: 84: /** 85: * Public constructor for use from outside this package. 86: * 87: * @param N the public shared modulus. 88: * @param g the generator. 89: * @param x the private exponent of the ephemeral key. 90: * @param v the user's verifier value (for the server side only). 91: */ 92: public SRPPrivateKey(BigInteger N, BigInteger g, BigInteger x, BigInteger v) 93: { 94: super(N, g); 95: 96: SRPAlgorithm.checkParams(N, g); 97: this.X = x; 98: this.v = v; 99: } 100: 101: /** 102: * Default constructor. Assumes N and g are already validated. 103: * 104: * @param params an array of either 3 or 4 values representing N, g, and 105: * either v and X for the server, or just X for the client. Those 106: * values represent the following: 107: * <ol> 108: * <li>v (server side): the user's verifier.</li> 109: * <li>X (both sides): the server's or client's ephemeral private 110: * exponent.</li> 111: * </ol> 112: */ 113: SRPPrivateKey(BigInteger[] params) 114: { 115: super(params[0], params[1]); 116: 117: if (params.length == 3) 118: { 119: X = params[2]; 120: v = null; 121: } 122: else if (params.length == 4) 123: { 124: X = params[2]; 125: v = params[3]; 126: } 127: else 128: throw new IllegalArgumentException("invalid number of SRP parameters"); 129: } 130: 131: /** 132: * A class method that takes the output of the <code>encodePrivateKey()</code> 133: * method of an SRP keypair codec object (an instance implementing 134: * {@link IKeyPairCodec} for DSS keys, and re-constructs an instance of this 135: * object. 136: * 137: * @param k the contents of a previously encoded instance of this object. 138: * @throws ArrayIndexOutOfBoundsException if there is not enough bytes, in 139: * <code>k</code>, to represent a valid encoding of an instance 140: * of this object. 141: * @throws IllegalArgumentException if the byte sequence does not represent a 142: * valid encoding of an instance of this object. 143: */ 144: public static SRPPrivateKey valueOf(byte[] k) 145: { 146: // check magic... 147: // we should parse here enough bytes to know which codec to use, and 148: // direct the byte array to the appropriate codec. since we only have one 149: // codec, we could have immediately tried it; nevertheless since testing 150: // one byte is cheaper than instatiating a codec that will fail we test 151: // the first byte before we carry on. 152: if (k[0] == Registry.MAGIC_RAW_SRP_PRIVATE_KEY[0]) 153: { 154: // it's likely to be in raw format. get a raw codec and hand it over 155: IKeyPairCodec codec = new SRPKeyPairRawCodec(); 156: return (SRPPrivateKey) codec.decodePrivateKey(k); 157: } 158: throw new IllegalArgumentException("magic"); 159: } 160: 161: /** 162: * Returns the private exponent of the key as a {@link BigInteger}. 163: * 164: * @return the private exponent of the key as a {@link BigInteger}. 165: */ 166: public BigInteger getX() 167: { 168: return X; 169: } 170: 171: /** 172: * Returns the user's verifier as a {@link BigInteger}. 173: * 174: * @return the user's verifier as a {@link BigInteger} if this is an SRP 175: * private key of a Host, or <code>null</code> if this is a private 176: * SRP key for a User. 177: */ 178: public BigInteger getV() 179: { 180: return v; 181: } 182: 183: /** 184: * Returns the encoded form of this private key according to the designated 185: * format. 186: * 187: * @param format the desired format identifier of the resulting encoding. 188: * @return the byte sequence encoding this key according to the designated 189: * format. 190: * @throws IllegalArgumentException if the format is not supported. 191: */ 192: public byte[] getEncoded(int format) 193: { 194: byte[] result; 195: switch (format) 196: { 197: case IKeyPairCodec.RAW_FORMAT: 198: result = new SRPKeyPairRawCodec().encodePrivateKey(this); 199: break; 200: default: 201: throw new IllegalArgumentException("format"); 202: } 203: return result; 204: } 205: 206: /** 207: * Returns <code>true</code> if the designated object is an instance of 208: * <code>SRPPrivateKey</code> and has the same SRP parameter values as this 209: * one. 210: * 211: * @param obj the other non-null SRP key to compare to. 212: * @return <code>true</code> if the designated object is of the same type 213: * and value as this one. 214: */ 215: public boolean equals(Object obj) 216: { 217: if (obj == null) 218: return false; 219: if (! (obj instanceof SRPPrivateKey)) 220: return false; 221: SRPPrivateKey that = (SRPPrivateKey) obj; 222: boolean result = super.equals(that) && X.equals(that.getX()); 223: if (v != null) 224: result = result && v.equals(that.getV()); 225: return result; 226: } 227: }