From 120b36750e6c8287d8d9a12111177a66e1f52c38 Mon Sep 17 00:00:00 2001
From: Ethan Fast <Ejhfast@gmail.com>
Date: Sun, 27 Aug 2017 22:03:41 +1000
Subject: [PATCH] add nep2 support

---
 src/nep2.js | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 src/nep2.js

diff --git a/src/nep2.js b/src/nep2.js
new file mode 100644
index 000000000..60e4096be
--- /dev/null
+++ b/src/nep2.js
@@ -0,0 +1,87 @@
+// this code draws heavily from functions written originally by snowypowers
+
+import bs58check from 'bs58check';
+import wif from 'wif';
+import { SHA256, AES, enc } from 'crypto-js'
+import C from 'crypto-js'
+import scrypt from 'js-scrypt'
+import { getAccountsFromWIFKey, getAccountsFromPrivateKey, generatePrivateKey, getWIFFromPrivateKey } from './wallet';
+import { ab2hexstring, hexXor } from './utils';
+
+const NEP_HEADER = "0142"
+const NEP_FLAG = "e0"
+
+// specified by nep2, same as bip38
+const scrypt_options = {
+  cost: 16384,
+  blockSize: 8,
+  parallel: 8,
+  size: 64
+};
+
+// generate new encrypted wif given passphrase
+// (returns a promise)
+export const generateEncryptedWif = (passphrase) => {
+  const newPrivateKey = generatePrivateKey();
+  const newWif = getWIFFromPrivateKey(newPrivateKey);
+  return encrypt_wif(newWif, passphrase).then((encWif) => {
+    const loadAccount = getAccountsFromWIFKey(newWif);
+    return {
+      wif: newWif,
+      address: loadAccount[0].address,
+      encryptedWif: encWif,
+      passphrase: passphrase
+    };
+  });
+};
+
+// encrypt wif using keyphrase under nep2 standard
+// returns encrypted wif
+const encrypt = (wifKey, keyphrase, progressCallback) => {
+    const address = getAccountsFromWIFKey(wifKey)[0].address
+    const privateKey = getAccountsFromWIFKey(wifKey)[0].privatekey
+    // SHA Salt (use the first 4 bytes)
+    const addressHash = SHA256(SHA256(enc.Latin1.parse(address))).toString().slice(0, 8)
+    // Scrypt
+    const derived = scrypt.hashSync(Buffer.from(keyphrase, 'utf8'), Buffer.from(addressHash, 'hex'), scrypt_options, progressCallback).toString('hex')
+    const derived1 = derived.slice(0, 64)
+    const derived2 = derived.slice(64)
+    //AES Encrypt
+    const xor = hexXor(privateKey, derived1)
+    const encrypted = AES.encrypt(enc.Hex.parse(xor), enc.Hex.parse(derived2), { mode: C.mode.ECB, padding: C.pad.NoPadding })
+    //Construct
+    const assembled = NEP_HEADER + NEP_FLAG + addressHash + encrypted.ciphertext.toString()
+    return bs58check.encode(Buffer.from(assembled, 'hex'))
+};
+
+// decrypt encrypted wif using keyphrase under nep2 standard
+// returns wif
+const decrypt = (encryptedKey, keyphrase, progressCallback) => {
+    const assembled = ab2hexstring(bs58check.decode(encryptedKey))
+    const addressHash = assembled.substr(6, 8)
+    const encrypted = assembled.substr(-64)
+    const derived = scrypt.hashSync(Buffer.from(keyphrase, 'utf8'), Buffer.from(addressHash, 'hex'), scrypt_options, progressCallback).toString('hex')
+    const derived1 = derived.slice(0, 64)
+    const derived2 = derived.slice(64)
+    const ciphertext = { ciphertext: enc.Hex.parse(encrypted), salt: "" }
+    const decrypted = AES.decrypt(ciphertext, enc.Hex.parse(derived2), { mode: C.mode.ECB, padding: C.pad.NoPadding })
+    const privateKey = hexXor(decrypted.toString(), derived1)
+    const address = getAccountsFromPrivateKey(privateKey)[0].address
+    const newAddressHash = SHA256(SHA256(enc.Latin1.parse(address))).toString().slice(0, 8)
+    if (addressHash !== newAddressHash) throw new Error("Wrong Password!")
+    return getWIFFromPrivateKey(Buffer.from(privateKey, 'hex'));
+};
+
+// helpers to wrap synchronous functions in promises
+
+export const encrypt_wif = (wif, passphrase) => {
+  return (new Promise((success, reject) => {
+    success(encrypt(wif, passphrase));
+  }));
+};
+
+export const decrypt_wif = (encrypted_wif, passphrase) => {
+  return (new Promise((success, reject) => {
+    success(decrypt(encrypted_wif, passphrase));
+  }));
+};