diff options
Diffstat (limited to 'src/bech32.cpp')
| -rw-r--r-- | src/bech32.cpp | 44 |
1 files changed, 26 insertions, 18 deletions
diff --git a/src/bech32.cpp b/src/bech32.cpp index 1e0471f110..289e0213e8 100644 --- a/src/bech32.cpp +++ b/src/bech32.cpp @@ -1,4 +1,4 @@ -// Copyright (c) 2017 Pieter Wuille +// Copyright (c) 2017, 2021 Pieter Wuille // Distributed under the MIT software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. @@ -7,6 +7,9 @@ #include <assert.h> +namespace bech32 +{ + namespace { @@ -27,6 +30,12 @@ const int8_t CHARSET_REV[128] = { 1, 0, 3, 16, 11, 28, 12, 14, 6, 4, 2, -1, -1, -1, -1, -1 }; +/* Determine the final constant to use for the specified encoding. */ +uint32_t EncodingConstant(Encoding encoding) { + assert(encoding == Encoding::BECH32 || encoding == Encoding::BECH32M); + return encoding == Encoding::BECH32 ? 1 : 0x2bc830a3; +} + /** This function will compute what 6 5-bit values to XOR into the last 6 input values, in order to * make the checksum 0. These 6 values are packed together in a single 30-bit integer. The higher * bits correspond to earlier values. */ @@ -111,21 +120,24 @@ data ExpandHRP(const std::string& hrp) } /** Verify a checksum. */ -bool VerifyChecksum(const std::string& hrp, const data& values) +Encoding VerifyChecksum(const std::string& hrp, const data& values) { // PolyMod computes what value to xor into the final values to make the checksum 0. However, // if we required that the checksum was 0, it would be the case that appending a 0 to a valid // list of values would result in a new valid list. For that reason, Bech32 requires the - // resulting checksum to be 1 instead. - return PolyMod(Cat(ExpandHRP(hrp), values)) == 1; + // resulting checksum to be 1 instead. In Bech32m, this constant was amended. + const uint32_t check = PolyMod(Cat(ExpandHRP(hrp), values)); + if (check == EncodingConstant(Encoding::BECH32)) return Encoding::BECH32; + if (check == EncodingConstant(Encoding::BECH32M)) return Encoding::BECH32M; + return Encoding::INVALID; } /** Create a checksum. */ -data CreateChecksum(const std::string& hrp, const data& values) +data CreateChecksum(Encoding encoding, const std::string& hrp, const data& values) { data enc = Cat(ExpandHRP(hrp), values); enc.resize(enc.size() + 6); // Append 6 zeroes - uint32_t mod = PolyMod(enc) ^ 1; // Determine what to XOR into those 6 zeroes. + uint32_t mod = PolyMod(enc) ^ EncodingConstant(encoding); // Determine what to XOR into those 6 zeroes. data ret(6); for (size_t i = 0; i < 6; ++i) { // Convert the 5-bit groups in mod to checksum values. @@ -136,16 +148,13 @@ data CreateChecksum(const std::string& hrp, const data& values) } // namespace -namespace bech32 -{ - -/** Encode a Bech32 string. */ -std::string Encode(const std::string& hrp, const data& values) { +/** Encode a Bech32 or Bech32m string. */ +std::string Encode(Encoding encoding, const std::string& hrp, const data& values) { // First ensure that the HRP is all lowercase. BIP-173 requires an encoder // to return a lowercase Bech32 string, but if given an uppercase HRP, the // result will always be invalid. for (const char& c : hrp) assert(c < 'A' || c > 'Z'); - data checksum = CreateChecksum(hrp, values); + data checksum = CreateChecksum(encoding, hrp, values); data combined = Cat(values, checksum); std::string ret = hrp + '1'; ret.reserve(ret.size() + combined.size()); @@ -155,8 +164,8 @@ std::string Encode(const std::string& hrp, const data& values) { return ret; } -/** Decode a Bech32 string. */ -std::pair<std::string, data> Decode(const std::string& str) { +/** Decode a Bech32 or Bech32m string. */ +DecodeResult Decode(const std::string& str) { bool lower = false, upper = false; for (size_t i = 0; i < str.size(); ++i) { unsigned char c = str[i]; @@ -183,10 +192,9 @@ std::pair<std::string, data> Decode(const std::string& str) { for (size_t i = 0; i < pos; ++i) { hrp += LowerCase(str[i]); } - if (!VerifyChecksum(hrp, values)) { - return {}; - } - return {hrp, data(values.begin(), values.end() - 6)}; + Encoding result = VerifyChecksum(hrp, values); + if (result == Encoding::INVALID) return {}; + return {result, std::move(hrp), data(values.begin(), values.end() - 6)}; } } // namespace bech32 |