| 1 | var elliptic = require('elliptic')
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| 2 | var BN = require('bn.js')
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| 3 |
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| 4 | module.exports = function createECDH (curve) {
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| 5 | return new ECDH(curve)
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| 6 | }
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| 7 |
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| 8 | var aliases = {
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| 9 | secp256k1: {
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| 10 | name: 'secp256k1',
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| 11 | byteLength: 32
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| 12 | },
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| 13 | secp224r1: {
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| 14 | name: 'p224',
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| 15 | byteLength: 28
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| 16 | },
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| 17 | prime256v1: {
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| 18 | name: 'p256',
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| 19 | byteLength: 32
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| 20 | },
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| 21 | prime192v1: {
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| 22 | name: 'p192',
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| 23 | byteLength: 24
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| 24 | },
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| 25 | ed25519: {
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| 26 | name: 'ed25519',
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| 27 | byteLength: 32
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| 28 | },
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| 29 | secp384r1: {
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| 30 | name: 'p384',
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| 31 | byteLength: 48
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| 32 | },
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| 33 | secp521r1: {
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| 34 | name: 'p521',
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| 35 | byteLength: 66
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| 36 | }
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| 37 | }
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| 38 |
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| 39 | aliases.p224 = aliases.secp224r1
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| 40 | aliases.p256 = aliases.secp256r1 = aliases.prime256v1
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| 41 | aliases.p192 = aliases.secp192r1 = aliases.prime192v1
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| 42 | aliases.p384 = aliases.secp384r1
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| 43 | aliases.p521 = aliases.secp521r1
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| 44 |
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| 45 | function ECDH (curve) {
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| 46 | this.curveType = aliases[curve]
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| 47 | if (!this.curveType) {
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| 48 | this.curveType = {
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| 49 | name: curve
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| 50 | }
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| 51 | }
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| 52 | this.curve = new elliptic.ec(this.curveType.name)
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| 53 | this.keys = void 0
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| 54 | }
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| 55 |
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| 56 | ECDH.prototype.generateKeys = function (enc, format) {
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| 57 | this.keys = this.curve.genKeyPair()
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| 58 | return this.getPublicKey(enc, format)
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| 59 | }
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| 60 |
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| 61 | ECDH.prototype.computeSecret = function (other, inenc, enc) {
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| 62 | inenc = inenc || 'utf8'
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| 63 | if (!Buffer.isBuffer(other)) {
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| 64 | other = new Buffer(other, inenc)
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| 65 | }
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| 66 | var otherPub = this.curve.keyFromPublic(other).getPublic()
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| 67 | var out = otherPub.mul(this.keys.getPrivate()).getX()
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| 68 | return formatReturnValue(out, enc, this.curveType.byteLength)
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| 69 | }
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| 70 |
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| 71 | ECDH.prototype.getPublicKey = function (enc, format) {
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| 72 | var key = this.keys.getPublic(format === 'compressed', true)
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| 73 | if (format === 'hybrid') {
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| 74 | if (key[key.length - 1] % 2) {
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| 75 | key[0] = 7
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| 76 | } else {
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| 77 | key[0] = 6
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| 78 | }
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| 79 | }
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| 80 | return formatReturnValue(key, enc)
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| 81 | }
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| 82 |
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| 83 | ECDH.prototype.getPrivateKey = function (enc) {
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| 84 | return formatReturnValue(this.keys.getPrivate(), enc)
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| 85 | }
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| 86 |
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| 87 | ECDH.prototype.setPublicKey = function (pub, enc) {
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| 88 | enc = enc || 'utf8'
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| 89 | if (!Buffer.isBuffer(pub)) {
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| 90 | pub = new Buffer(pub, enc)
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| 91 | }
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| 92 | this.keys._importPublic(pub)
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| 93 | return this
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| 94 | }
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| 95 |
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| 96 | ECDH.prototype.setPrivateKey = function (priv, enc) {
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| 97 | enc = enc || 'utf8'
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| 98 | if (!Buffer.isBuffer(priv)) {
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| 99 | priv = new Buffer(priv, enc)
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| 100 | }
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| 101 |
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| 102 | var _priv = new BN(priv)
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| 103 | _priv = _priv.toString(16)
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| 104 | this.keys = this.curve.genKeyPair()
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| 105 | this.keys._importPrivate(_priv)
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| 106 | return this
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| 107 | }
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| 108 |
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| 109 | function formatReturnValue (bn, enc, len) {
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| 110 | if (!Array.isArray(bn)) {
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| 111 | bn = bn.toArray()
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| 112 | }
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| 113 | var buf = new Buffer(bn)
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| 114 | if (len && buf.length < len) {
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| 115 | var zeros = new Buffer(len - buf.length)
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| 116 | zeros.fill(0)
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| 117 | buf = Buffer.concat([zeros, buf])
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| 118 | }
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| 119 | if (!enc) {
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| 120 | return buf
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| 121 | } else {
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| 122 | return buf.toString(enc)
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| 123 | }
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| 124 | }
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