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2 package com.trilead.ssh2.signature;
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3
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4 import java.io.IOException;
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5 import java.math.BigInteger;
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6 import java.security.InvalidKeyException;
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7 import java.security.KeyFactory;
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8 import java.security.NoSuchAlgorithmException;
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9 import java.security.SecureRandom;
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10 import java.security.Signature;
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11 import java.security.SignatureException;
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12 import java.security.interfaces.DSAParams;
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13 import java.security.interfaces.DSAPrivateKey;
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14 import java.security.interfaces.DSAPublicKey;
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15 import java.security.spec.DSAPublicKeySpec;
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16 import java.security.spec.InvalidKeySpecException;
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17 import java.security.spec.KeySpec;
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18
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19 import com.trilead.ssh2.log.Logger;
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20 import com.trilead.ssh2.packets.TypesReader;
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21 import com.trilead.ssh2.packets.TypesWriter;
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22
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23
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24 /**
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25 * DSASHA1Verify.
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26 *
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27 * @author Christian Plattner, plattner@trilead.com
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28 * @version $Id: DSASHA1Verify.java,v 1.2 2008/04/01 12:38:09 cplattne Exp $
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29 */
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30 public class DSASHA1Verify {
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31 private static final Logger log = Logger.getLogger(DSASHA1Verify.class);
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32
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33 public static DSAPublicKey decodeSSHDSAPublicKey(byte[] key) throws IOException {
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34 TypesReader tr = new TypesReader(key);
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35 String key_format = tr.readString();
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36
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37 if (key_format.equals("ssh-dss") == false)
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38 throw new IllegalArgumentException("This is not a ssh-dss public key!");
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39
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40 BigInteger p = tr.readMPINT();
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41 BigInteger q = tr.readMPINT();
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42 BigInteger g = tr.readMPINT();
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43 BigInteger y = tr.readMPINT();
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44
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45 if (tr.remain() != 0)
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46 throw new IOException("Padding in DSA public key!");
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47
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48 try {
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49 KeyFactory kf = KeyFactory.getInstance("DSA");
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50 KeySpec ks = new DSAPublicKeySpec(y, p, q, g);
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51 return (DSAPublicKey) kf.generatePublic(ks);
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52 }
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53 catch (NoSuchAlgorithmException e) {
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54 IOException ex = new IOException();
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55 ex.initCause(e);
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56 throw ex;
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57 }
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58 catch (InvalidKeySpecException e) {
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59 IOException ex = new IOException();
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60 ex.initCause(e);
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61 throw ex;
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62 }
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63 }
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64
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65 public static byte[] encodeSSHDSAPublicKey(DSAPublicKey pk) throws IOException {
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66 TypesWriter tw = new TypesWriter();
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67 tw.writeString("ssh-dss");
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68 DSAParams params = pk.getParams();
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69 tw.writeMPInt(params.getP());
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70 tw.writeMPInt(params.getQ());
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71 tw.writeMPInt(params.getG());
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72 tw.writeMPInt(pk.getY());
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73 return tw.getBytes();
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74 }
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75
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76 /**
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77 * Convert from Java's signature ASN.1 encoding to the SSH spec.
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78 * <p>
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79 * Java ASN.1 encoding:
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80 * <pre>
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81 * SEQUENCE ::= {
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82 * r INTEGER,
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83 * s INTEGER
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84 * }
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85 * </pre>
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86 */
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87 public static byte[] encodeSSHDSASignature(byte[] ds) {
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88 TypesWriter tw = new TypesWriter();
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89 tw.writeString("ssh-dss");
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90 int len, index;
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91 index = 3;
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92 len = ds[index++] & 0xff;
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93 byte[] r = new byte[len];
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94 System.arraycopy(ds, index, r, 0, r.length);
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95 index = index + len + 1;
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96 len = ds[index++] & 0xff;
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97 byte[] s = new byte[len];
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98 System.arraycopy(ds, index, s, 0, s.length);
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99 byte[] a40 = new byte[40];
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100 /* Patch (unsigned) r and s into the target array. */
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101 int r_copylen = (r.length < 20) ? r.length : 20;
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102 int s_copylen = (s.length < 20) ? s.length : 20;
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103 System.arraycopy(r, r.length - r_copylen, a40, 20 - r_copylen, r_copylen);
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104 System.arraycopy(s, s.length - s_copylen, a40, 40 - s_copylen, s_copylen);
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105 tw.writeString(a40, 0, 40);
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106 return tw.getBytes();
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107 }
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108
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109 public static byte[] decodeSSHDSASignature(byte[] sig) throws IOException {
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110 byte[] rsArray = null;
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111
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112 if (sig.length == 40) {
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113 /* OK, another broken SSH server. */
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114 rsArray = sig;
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115 }
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116 else {
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117 /* Hopefully a server obeying the standard... */
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118 TypesReader tr = new TypesReader(sig);
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119 String sig_format = tr.readString();
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120
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121 if (sig_format.equals("ssh-dss") == false)
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122 throw new IOException("Peer sent wrong signature format");
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123
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124 rsArray = tr.readByteString();
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125
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126 if (rsArray.length != 40)
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127 throw new IOException("Peer sent corrupt signature");
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128
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129 if (tr.remain() != 0)
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130 throw new IOException("Padding in DSA signature!");
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131 }
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132
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133 int i = 0;
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134 int j = 0;
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135 byte[] tmp;
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136
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137 if (rsArray[0] == 0 && rsArray[1] == 0 && rsArray[2] == 0) {
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138 j = ((rsArray[i++] << 24) & 0xff000000) | ((rsArray[i++] << 16) & 0x00ff0000)
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139 | ((rsArray[i++] << 8) & 0x0000ff00) | ((rsArray[i++]) & 0x000000ff);
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140 i += j;
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141 j = ((rsArray[i++] << 24) & 0xff000000) | ((rsArray[i++] << 16) & 0x00ff0000)
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142 | ((rsArray[i++] << 8) & 0x0000ff00) | ((rsArray[i++]) & 0x000000ff);
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143 tmp = new byte[j];
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144 System.arraycopy(rsArray, i, tmp, 0, j);
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145 rsArray = tmp;
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146 }
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147
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148 /* ASN.1 */
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149 int frst = ((rsArray[0] & 0x80) != 0 ? 1 : 0);
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150 int scnd = ((rsArray[20] & 0x80) != 0 ? 1 : 0);
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151 /* Calculate output length */
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152 int length = rsArray.length + 6 + frst + scnd;
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153 tmp = new byte[length];
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154 /* DER-encoding to match Java */
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155 tmp[0] = (byte) 0x30;
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156
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157 if (rsArray.length != 40)
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158 throw new IOException("Peer sent corrupt signature");
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159
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160 /* Calculate length */
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161 tmp[1] = (byte) 0x2c;
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162 tmp[1] += frst;
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163 tmp[1] += scnd;
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164 /* First item */
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165 tmp[2] = (byte) 0x02;
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166 /* First item length */
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167 tmp[3] = (byte) 0x14;
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168 tmp[3] += frst;
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169 /* Copy in the data for first item */
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170 System.arraycopy(rsArray, 0, tmp, 4 + frst, 20);
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171 /* Second item */
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172 tmp[4 + tmp[3]] = (byte) 0x02;
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173 /* Second item length */
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174 tmp[5 + tmp[3]] = (byte) 0x14;
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175 tmp[5 + tmp[3]] += scnd;
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176 /* Copy in the data for the second item */
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177 System.arraycopy(rsArray, 20, tmp, 6 + tmp[3] + scnd, 20);
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178 /* Swap buffers */
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179 rsArray = tmp;
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180 return rsArray;
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181 }
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182
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183 public static boolean verifySignature(byte[] message, byte[] ds, DSAPublicKey dpk) throws IOException {
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184 try {
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185 Signature s = Signature.getInstance("SHA1withDSA");
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186 s.initVerify(dpk);
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187 s.update(message);
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188 return s.verify(ds);
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189 }
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190 catch (NoSuchAlgorithmException e) {
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191 IOException ex = new IOException("No such algorithm");
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192 ex.initCause(e);
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193 throw ex;
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194 }
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195 catch (InvalidKeyException e) {
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196 IOException ex = new IOException("No such algorithm");
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197 ex.initCause(e);
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198 throw ex;
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199 }
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200 catch (SignatureException e) {
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201 IOException ex = new IOException();
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202 ex.initCause(e);
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203 throw ex;
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204 }
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205 }
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206
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207 public static byte[] generateSignature(byte[] message, DSAPrivateKey pk, SecureRandom rnd) throws IOException {
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208 try {
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209 Signature s = Signature.getInstance("SHA1withDSA");
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210 s.initSign(pk);
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211 s.update(message);
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212 return s.sign();
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213 }
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214 catch (NoSuchAlgorithmException e) {
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215 IOException ex = new IOException();
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216 ex.initCause(e);
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217 throw ex;
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218 }
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219 catch (InvalidKeyException e) {
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220 IOException ex = new IOException();
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221 ex.initCause(e);
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222 throw ex;
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223 }
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224 catch (SignatureException e) {
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225 IOException ex = new IOException();
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226 ex.initCause(e);
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227 throw ex;
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228 }
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229 }
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230 }
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