added message sign and verify functionality

README.md

@@ -209,6 +209,47 @@ var Zaddress = zencashjs.zaddress.mkZAddress(a_pk, pk_enc)
 // zcTPZR8Hqz2ZcStwMJju9L4VBHW7YWmNyL6tDAT4eVmzmxLaG7h4QmqUXfmrjz8twizH4piDGiRYJRZ1bhHhT5gFL6TKsQZ
 ```
 
+# Example usage (Sign/Verify message)
+```javascript
+var zencashjs = require('zencashjs')
+
+var priv = zencashjs.address.mkPrivKey('chris p. bacon, defender of the guardians')
+// 2c3a48576fe6e8a466e78cd2957c9dc62128135540bbea0685d7c4a23ea35a6c
+
+var privWIF = zencashjs.address.privKeyToWIF(priv)
+// 5J9mKPd531Tk4A73kKp4iowoi6EvhEp8QSMAVzrZhuzZkdpYbK8
+
+var pubKey = zencashjs.address.privKeyToPubKey(priv, true) // generate compressed pubKey
+// 038a789e0910b6aa314f63d2cc666bd44fa4b71d7397cb5466902dc594c1a0a0d2
+
+var zAddr = zencashjs.address.pubKeyToAddr(pubKey)
+// znnjppzJG7ajT7f6Vp1AD6SjgcXBVPA2E6c
+
+var message = 'ciao'
+
+/**
+ * Will sign a message with a given zen private key.
+ *
+ * @param {string} message - The message to be signed
+ * @param {string} privateKey - A private key
+ * @param {Boolean} compressed
+ * @returns {Buffer} The signature
+ */
+var signature = zencashjs.message.sign(message, priv, true)
+// signature.toString('base64')
+// IC7SPUlfyjKjG7hrrPWc6WTsm79ksjHAYXSFmjlGwAL9SSvAIvpYmOm3U5CzG2k0QBxDYuzpltw+UAET3J8e7Gg=
+
+/**
+ * Validate a signature against a given zend address.
+ *
+ * @param {String} message - the message to verify
+ * @param {String} zenAddress - A zen address
+ * @param {String|Buffer} signature - A base64 encoded compact signature
+ * @returns {Boolean} true if the signature is valid
+ */
+var verification = zencashjs.message.verify(message, zAddr, signature)
+ // true
+```
 
 # Development guide (more to come..)
 ```bash

lib/crypto.js

@@ -1,5 +1,9 @@
 "use strict";
 
+var _module$exports;
+
+function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+
 /* 
  * Obtained from https://github.com/bitcoinjs/bitcoinjs-lib/blob/master/src/crypto.js
  * 2017/07/25: No ripemd160 in SJCL, so resorted to this
@@ -28,10 +32,22 @@ function hash160(buffer) {
   return hash160;
 }
 
-module.exports = {
+function sha256Buf(buffer) {
+  return createHash('sha256').update(buffer).digest();
+}
+
+function hash256Buf(buffer) {
+  return sha256Buf(sha256Buf(buffer));
+}
+
+function hash160Buf(buffer) {
+  return createHash('ripemd160').update(sha256Buf(buffer)).digest();
+}
+
+module.exports = (_module$exports = {
   hash160: hash160,
   ripemd160: ripemd160,
   sha1: sha1,
   sha256: sha256,
   sha256x2: sha256x2
-};
+}, _defineProperty(_module$exports, "sha256x2", sha256x2), _defineProperty(_module$exports, "hash256Buf", hash256Buf), _defineProperty(_module$exports, "hash160Buf", hash160Buf), _module$exports);

lib/index.js

@@ -6,5 +6,6 @@ module.exports = {
   zaddress: require('./zaddress'),
   crypto: require('./crypto'),
   transaction: require('./transaction'),
-  bufferutils: require('./bufferutils')
+  bufferutils: require('./bufferutils'),
+  message: require('./message')
 };

lib/message.js

@@ -0,0 +1,88 @@
+"use strict";
+
+var bs58check = require('bs58check');
+
+var secp256k1 = require('secp256k1');
+
+var zcrypto = require('./crypto');
+
+var varuint = require('varuint-bitcoin');
+/**
+ * Will sign a message with a given zen private key.
+ *
+ * @param {string} message - The message to be signed
+ * @param {string} privateKey - A private key
+ * @param {Boolean} compressed
+ * @returns {Buffer} The signature
+ */
+
+
+function sign(message, privateKey, compressed, sigOptions) {
+  var _ref = sigOptions || {},
+      extraEntropy = _ref.extraEntropy;
+
+  var hash = _magicHash(message, false);
+
+  var sigObj = secp256k1.sign(hash, Buffer.from(privateKey, 'hex'), {
+    data: extraEntropy
+  });
+  return encodeSignature(sigObj.signature, sigObj.recovery, compressed);
+}
+/**
+ * Validate a signature against a given zend address.
+ *
+ * @param {String} message - the message to verify
+ * @param {String} zenAddress - A zen address
+ * @param {String|Buffer} signature - A base64 encoded compact signature
+ * @returns {Boolean} true if the signature is valid
+ */
+
+
+function verify(message, zenAddress, signature) {
+  if (!Buffer.isBuffer(signature)) signature = Buffer.from(signature, 'base64');
+  var parsed = decodeSignature(signature);
+
+  var hash = _magicHash(message, false);
+
+  var publicKey = secp256k1.recover(hash, parsed.signature, parsed.recovery, parsed.compressed);
+  var publicKeyHash = zcrypto.hash160Buf(publicKey);
+  var actual, expected;
+  actual = publicKeyHash; // prefix is 2 bytes in zencash instead of 1 
+
+  expected = bs58check.decode(zenAddress).slice(2);
+  return expected.equals(actual);
+}
+
+function encodeSignature(signature, recovery, compressed) {
+  if (compressed) recovery += 4;
+  return Buffer.concat([Buffer.alloc(1, recovery + 27), signature]);
+}
+
+function decodeSignature(buffer) {
+  if (buffer.length !== 65) throw new Error('Invalid signature length');
+  var flagByte = buffer.readUInt8(0) - 27;
+
+  if (flagByte > 15 || flagByte < 0) {
+    throw new Error('Invalid signature parameter');
+  }
+
+  return {
+    compressed: !!(flagByte & 12),
+    recovery: flagByte & 3,
+    signature: buffer.slice(1)
+  };
+}
+
+function _magicHash(message) {
+  var MAGIC_BYTES = Buffer.from('Zcash Signed Message:\n', 'utf8');
+  var prefix1 = varuint.encode(MAGIC_BYTES.length);
+  var messageBuffer = Buffer.from(message, 'utf8');
+  var prefix2 = varuint.encode(messageBuffer.length);
+  var buf = Buffer.concat([prefix1, MAGIC_BYTES, prefix2, messageBuffer]);
+  return zcrypto.hash256Buf(buf);
+}
+
+module.exports = {
+  sign: sign,
+  verify: verify
+};