var elliptic = require('elliptic')
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var BN = require('bn.js')
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module.exports = function createECDH (curve) {
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return new ECDH(curve)
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}
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var aliases = {
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secp256k1: {
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name: 'secp256k1',
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byteLength: 32
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},
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secp224r1: {
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name: 'p224',
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byteLength: 28
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},
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prime256v1: {
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name: 'p256',
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byteLength: 32
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},
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prime192v1: {
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name: 'p192',
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byteLength: 24
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},
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ed25519: {
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name: 'ed25519',
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byteLength: 32
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},
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secp384r1: {
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name: 'p384',
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byteLength: 48
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},
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secp521r1: {
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name: 'p521',
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byteLength: 66
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}
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}
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aliases.p224 = aliases.secp224r1
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aliases.p256 = aliases.secp256r1 = aliases.prime256v1
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aliases.p192 = aliases.secp192r1 = aliases.prime192v1
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aliases.p384 = aliases.secp384r1
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aliases.p521 = aliases.secp521r1
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function ECDH (curve) {
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this.curveType = aliases[curve]
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if (!this.curveType) {
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this.curveType = {
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name: curve
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}
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}
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this.curve = new elliptic.ec(this.curveType.name) // eslint-disable-line new-cap
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this.keys = void 0
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}
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ECDH.prototype.generateKeys = function (enc, format) {
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this.keys = this.curve.genKeyPair()
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return this.getPublicKey(enc, format)
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}
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ECDH.prototype.computeSecret = function (other, inenc, enc) {
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inenc = inenc || 'utf8'
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if (!Buffer.isBuffer(other)) {
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other = new Buffer(other, inenc)
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}
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var otherPub = this.curve.keyFromPublic(other).getPublic()
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var out = otherPub.mul(this.keys.getPrivate()).getX()
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return formatReturnValue(out, enc, this.curveType.byteLength)
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}
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ECDH.prototype.getPublicKey = function (enc, format) {
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var key = this.keys.getPublic(format === 'compressed', true)
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if (format === 'hybrid') {
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if (key[key.length - 1] % 2) {
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key[0] = 7
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} else {
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key[0] = 6
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}
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}
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return formatReturnValue(key, enc)
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}
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ECDH.prototype.getPrivateKey = function (enc) {
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return formatReturnValue(this.keys.getPrivate(), enc)
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}
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ECDH.prototype.setPublicKey = function (pub, enc) {
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enc = enc || 'utf8'
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if (!Buffer.isBuffer(pub)) {
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pub = new Buffer(pub, enc)
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}
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this.keys._importPublic(pub)
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return this
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}
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ECDH.prototype.setPrivateKey = function (priv, enc) {
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enc = enc || 'utf8'
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if (!Buffer.isBuffer(priv)) {
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priv = new Buffer(priv, enc)
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}
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var _priv = new BN(priv)
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_priv = _priv.toString(16)
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this.keys = this.curve.genKeyPair()
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this.keys._importPrivate(_priv)
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return this
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}
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function formatReturnValue (bn, enc, len) {
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if (!Array.isArray(bn)) {
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bn = bn.toArray()
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}
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var buf = new Buffer(bn)
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if (len && buf.length < len) {
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var zeros = new Buffer(len - buf.length)
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zeros.fill(0)
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buf = Buffer.concat([zeros, buf])
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}
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if (!enc) {
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return buf
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} else {
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return buf.toString(enc)
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}
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}
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