Looking for a JavaScript Sapling address validator

BostonZcash · August 25, 2020, 11:24pm

Would someone know of a JavaScript validator for Sapling’s bech32 addresses?

Or, why might a BTC bech32 decoder complain that a Sapling address has ‘non-zero padding’:

https://github.com/bitcoinjs/bech32/blob/master/index.js#L144

Thanks!

secured2k · August 26, 2020, 1:22am

I do not know of any javascript validators for Zcash/Sapling addresses.

The BTC decoder is likely to complain because of changes in the format (such as address size) when compared to Zcash.

There is a lot of very technical documentation - starting with the protocol specification

The section you are asking about is around 5.6 → 5.6.4 which should lead you to ZIP-173.
https://zips.z.cash/zip-0173

Which will list the details zcash takes to use bech32. It also includes a reference encoder/decoder from zcashd source in bech32.cpp

github.com

zcash/zcash/blob/master/src/bech32.cpp

// Copyright (c) 2017 Pieter Wuille
// Distributed under the MIT software license, see the accompanying
// file COPYING or https://www.opensource.org/licenses/mit-license.php .

#include "bech32.h"

namespace
{

typedef std::vector<uint8_t> data;

/** The Bech32 character set for encoding. */
const char* CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l";

/** The Bech32 character set for decoding. */
const int8_t CHARSET_REV[128] = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    15, -1, 10, 17, 21, 20, 26, 30,  7,  5, -1, -1, -1, -1, -1, -1,

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BostonZcash · August 27, 2020, 10:56pm

Thanks for the swift reply! With some details from the ZIP, I was able to get validation working with the existing BTC library.