56 lines
1.6 KiB
JavaScript
56 lines
1.6 KiB
JavaScript
var Key = require('./Key'),
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Point = require('./Point'),
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twoSha256 = require('../util').twoSha256,
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buffertools = require('buffertools'),
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bignum = require('./Bignum');
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/**
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* Pre-BIP32 Electrum public key derivation (electrum <2.0)
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*
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* For now, this class can only understands master public keys.
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* It doesn't support derivation from a private master key (TODO).
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*
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* @example examples/ElectrumMPK.js
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*/
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function Electrum (master_public_key) {
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this.mpk = new Buffer(master_public_key, 'hex');
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}
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Electrum.prototype.getSequence = function (for_change, n) {
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var mode = for_change ? 1 : 0;
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var buf = Buffer.concat([ new Buffer(n + ':' + mode + ':', 'utf8'), this.mpk ]);
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return bignum.fromBuffer(twoSha256(buf));
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};
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Electrum.prototype.generatePubKey = function (n, for_change) {
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var x = bignum.fromBuffer(this.mpk.slice(0, 32), { size: 32 });
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var y = bignum.fromBuffer(this.mpk.slice(32, 64), { size: 32 });
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var mpk_pt = new Point(x, y);
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var sequence = this.getSequence(for_change, n);
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var sequence_key = new Key();
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sequence_key.private = sequence.toBuffer();
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sequence_key.regenerateSync();
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sequence_key.compressed = false;
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var sequence_pt = Point.fromUncompressedPubKey(sequence_key.public);
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pt = Point.add(mpk_pt, sequence_pt);
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var xbuf = pt.x.toBuffer({ size: 32 });
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var ybuf = pt.y.toBuffer({ size: 32 });
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var prefix = new Buffer([0x04]);
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var key = new Key();
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key.compressed = false;
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key.public = Buffer.concat([prefix, xbuf, ybuf]);
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return key.public;
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};
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Electrum.prototype.generateChangePubKey = function (sequence) {
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return this.generatePubKey(sequence, true);
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};
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module.exports = Electrum;
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