bitcoinjs-lib/src/message.js

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/// Implements Bitcoin's feature for signing arbitrary messages.
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var SHA256 = require('crypto-js/sha256')
var ecdsa = require('./ecdsa')
var convert = require('./convert')
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var Message = {}
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Message.magicPrefix = "Bitcoin Signed Message:\n"
Message.makeMagicMessage = function (message) {
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var magicBytes = convert.stringToBytes(Message.magicPrefix)
var messageBytes = convert.stringToBytes(message)
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return [].concat(
convert.numToVarInt(magicBytes.length),
magicBytes,
convert.numToVarInt(messageBytes.length),
messageBytes
)
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}
Message.getHash = function (message) {
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var buffer = Message.makeMagicMessage(message)
return convert.wordArrayToBytes(SHA256(SHA256(convert.bytesToWordArray(buffer))))
}
Message.signMessage = function (key, message) {
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var hash = Message.getHash(message)
var sig = key.sign(hash)
var obj = ecdsa.parseSig(sig)
var i = ecdsa.calcPubkeyRecoveryParam(key, obj.r, obj.s, hash)
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i += 27
if (key.compressed) {
i += 4
}
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var rBa = obj.r.toByteArrayUnsigned()
var sBa = obj.s.toByteArrayUnsigned()
// Pad to 32 bytes per value
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while (rBa.length < 32) rBa.unshift(0)
while (sBa.length < 32) sBa.unshift(0)
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sig = [i].concat(rBa, sBa)
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return convert.bytesToHex(sig)
}
Message.verifyMessage = function (address, sig, message) {
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sig = ecdsa.parseSigCompact(convert.hexToBytes(sig))
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var hash = Message.getHash(message)
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var isCompressed = !!(sig.i & 4)
var pubKey = ecdsa.recoverPubKey(sig.r, sig.s, hash, sig.i)
pubKey.compressed = isCompressed
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// Compare address to expected address
return address === pubKey.getAddress().toString()
}
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module.exports = Message