1 | var BN = require('bn.js');
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2 | var MillerRabin = require('miller-rabin');
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3 | var millerRabin = new MillerRabin();
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4 | var TWENTYFOUR = new BN(24);
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5 | var ELEVEN = new BN(11);
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6 | var TEN = new BN(10);
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7 | var THREE = new BN(3);
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8 | var SEVEN = new BN(7);
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9 | var primes = require('./generatePrime');
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10 | var randomBytes = require('randombytes');
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11 | module.exports = DH;
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12 |
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13 | function setPublicKey(pub, enc) {
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14 | enc = enc || 'utf8';
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15 | if (!Buffer.isBuffer(pub)) {
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16 | pub = new Buffer(pub, enc);
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17 | }
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18 | this._pub = new BN(pub);
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19 | return this;
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20 | }
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21 |
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22 | function setPrivateKey(priv, enc) {
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23 | enc = enc || 'utf8';
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24 | if (!Buffer.isBuffer(priv)) {
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25 | priv = new Buffer(priv, enc);
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26 | }
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27 | this._priv = new BN(priv);
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28 | return this;
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29 | }
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30 |
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31 | var primeCache = {};
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32 | function checkPrime(prime, generator) {
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33 | var gen = generator.toString('hex');
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34 | var hex = [gen, prime.toString(16)].join('_');
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35 | if (hex in primeCache) {
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36 | return primeCache[hex];
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37 | }
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38 | var error = 0;
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39 |
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40 | if (prime.isEven() ||
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41 | !primes.simpleSieve ||
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42 | !primes.fermatTest(prime) ||
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43 | !millerRabin.test(prime)) {
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44 |
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45 | error += 1;
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46 |
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47 | if (gen === '02' || gen === '05') {
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48 |
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49 |
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50 | error += 8;
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51 | } else {
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52 |
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53 |
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54 | error += 4;
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55 | }
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56 | primeCache[hex] = error;
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57 | return error;
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58 | }
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59 | if (!millerRabin.test(prime.shrn(1))) {
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60 |
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61 | error += 2;
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62 | }
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63 | var rem;
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64 | switch (gen) {
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65 | case '02':
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66 | if (prime.mod(TWENTYFOUR).cmp(ELEVEN)) {
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67 |
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68 | error += 8;
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69 | }
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70 | break;
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71 | case '05':
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72 | rem = prime.mod(TEN);
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73 | if (rem.cmp(THREE) && rem.cmp(SEVEN)) {
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74 |
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75 | error += 8;
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76 | }
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77 | break;
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78 | default:
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79 | error += 4;
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80 | }
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81 | primeCache[hex] = error;
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82 | return error;
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83 | }
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84 |
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85 | function DH(prime, generator, malleable) {
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86 | this.setGenerator(generator);
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87 | this.__prime = new BN(prime);
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88 | this._prime = BN.mont(this.__prime);
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89 | this._primeLen = prime.length;
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90 | this._pub = undefined;
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91 | this._priv = undefined;
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92 | this._primeCode = undefined;
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93 | if (malleable) {
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94 | this.setPublicKey = setPublicKey;
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95 | this.setPrivateKey = setPrivateKey;
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96 | } else {
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97 | this._primeCode = 8;
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98 | }
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99 | }
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100 | Object.defineProperty(DH.prototype, 'verifyError', {
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101 | enumerable: true,
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102 | get: function () {
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103 | if (typeof this._primeCode !== 'number') {
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104 | this._primeCode = checkPrime(this.__prime, this.__gen);
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105 | }
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106 | return this._primeCode;
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107 | }
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108 | });
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109 | DH.prototype.generateKeys = function () {
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110 | if (!this._priv) {
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111 | this._priv = new BN(randomBytes(this._primeLen));
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112 | }
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113 | this._pub = this._gen.toRed(this._prime).redPow(this._priv).fromRed();
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114 | return this.getPublicKey();
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115 | };
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116 |
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117 | DH.prototype.computeSecret = function (other) {
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118 | other = new BN(other);
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119 | other = other.toRed(this._prime);
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120 | var secret = other.redPow(this._priv).fromRed();
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121 | var out = new Buffer(secret.toArray());
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122 | var prime = this.getPrime();
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123 | if (out.length < prime.length) {
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124 | var front = new Buffer(prime.length - out.length);
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125 | front.fill(0);
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126 | out = Buffer.concat([front, out]);
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127 | }
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128 | return out;
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129 | };
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130 |
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131 | DH.prototype.getPublicKey = function getPublicKey(enc) {
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132 | return formatReturnValue(this._pub, enc);
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133 | };
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134 |
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135 | DH.prototype.getPrivateKey = function getPrivateKey(enc) {
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136 | return formatReturnValue(this._priv, enc);
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137 | };
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138 |
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139 | DH.prototype.getPrime = function (enc) {
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140 | return formatReturnValue(this.__prime, enc);
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141 | };
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142 |
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143 | DH.prototype.getGenerator = function (enc) {
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144 | return formatReturnValue(this._gen, enc);
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145 | };
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146 |
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147 | DH.prototype.setGenerator = function (gen, enc) {
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148 | enc = enc || 'utf8';
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149 | if (!Buffer.isBuffer(gen)) {
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150 | gen = new Buffer(gen, enc);
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151 | }
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152 | this.__gen = gen;
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153 | this._gen = new BN(gen);
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154 | return this;
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155 | };
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156 |
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157 | function formatReturnValue(bn, enc) {
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158 | var buf = new Buffer(bn.toArray());
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159 | if (!enc) {
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160 | return buf;
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161 | } else {
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162 | return buf.toString(enc);
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163 | }
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164 | }
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