Bech32.kt
/*
* This file is part of GNU Taler
* (C) 2020 Taler Systems S.A.
*
* GNU Taler is free software; you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation; either version 3, or (at your option) any later version.
*
* GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
* A PARTICULAR PURPOSE. See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along with
* GNU Taler; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
*/
// Copyright (c) 2020 Figure Technologies Inc.
// The contents of this file were derived from an implementation
// by the btcsuite developers https://github.com/btcsuite/btcutil.
// Copyright (c) 2017 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
// modified version of https://gist.github.com/iramiller/4ebfcdfbc332a9722c4a4abeb4e16454
package net.taler.common
import java.util.Locale.ROOT
import kotlin.experimental.and
import kotlin.experimental.or
infix fun Int.min(b: Int): Int = b.takeIf { this > b } ?: this
infix fun UByte.shl(bitCount: Int) = ((this.toInt() shl bitCount) and 0xff).toUByte()
infix fun UByte.shr(bitCount: Int) = (this.toInt() shr bitCount).toUByte()
/**
* Bech32 Data encoding instance containing data for encoding as well as a human readable prefix
*/
data class Bech32Data(val hrp: String, val fiveBitData: ByteArray) {
/**
* The encapsulated data as typical 8bit bytes.
*/
val data = Bech32.convertBits(fiveBitData, 5, 8, false)
/**
* Address is the Bech32 encoded value of the data prefixed with the human readable portion and
* protected by an appended checksum.
*/
val address = Bech32.encode(hrp, fiveBitData)
/**
* Checksum for encapsulated data + hrp
*/
val checksum = Bech32.checksum(this.hrp, this.fiveBitData.toTypedArray())
/**
* The Bech32 Address toString prints state information for debugging purposes.
* @see address() for the bech32 encoded address string output.
*/
override fun toString(): String {
return "bech32 : ${this.address}\nhuman: ${this.hrp} \nbytes"
}
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (javaClass != other?.javaClass) return false
other as Bech32Data
if (hrp != other.hrp) return false
if (!fiveBitData.contentEquals(other.fiveBitData)) return false
if (!data.contentEquals(other.data)) return false
if (address != other.address) return false
if (!checksum.contentEquals(other.checksum)) return false
return true
}
override fun hashCode(): Int {
var result = hrp.hashCode()
result = 31 * result + fiveBitData.contentHashCode()
result = 31 * result + data.contentHashCode()
result = 31 * result + address.hashCode()
result = 31 * result + checksum.contentHashCode()
return result
}
}
/**
* BIP173 compliant processing functions for handling Bech32 encoding for addresses
*/
class Bech32 {
companion object {
const val CHECKSUM_SIZE = 6
private const val MIN_VALID_LENGTH = 8
private const val MAX_VALID_LENGTH = 90
const val MIN_VALID_CODEPOINT = 33
private const val MAX_VALID_CODEPOINT = 126
const val charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
private val gen = intArrayOf(0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3)
fun generateFakeSegwitAddress(reservePub: String?, addr: String): List<String> {
if (reservePub == null || reservePub.isEmpty()) return listOf()
val pub = CyptoUtils.decodeCrock(reservePub)
if (pub.size != 32) return listOf()
val firstRnd = pub.copyOfRange(0, 4)
val secondRnd = pub.copyOfRange(0, 4)
firstRnd[0] = firstRnd[0].and(0b0111_1111)
secondRnd[0] = secondRnd[0].or(0b1000_0000.toByte())
val firstPart = ByteArray(20)
firstRnd.copyInto(firstPart, 0, 0, 4)
pub.copyInto(firstPart, 4, 0, 16)
val secondPart = ByteArray(20)
secondRnd.copyInto(secondPart, 0, 0, 4)
pub.copyInto(secondPart, 4, 16, 32)
val zero = ByteArray(1)
zero[0] = 0
val hrp = when {
addr[0] == 'b' && addr[1] == 'c' && addr[2] == 'r' && addr[3] == 't' -> "bcrt"
addr[0] == 't' && addr[1] == 'b' -> "tb"
addr[0] == 'b' && addr[1] == 'c' -> "bc"
else -> throw Error("unknown bitcoin net")
}
return listOf(
Bech32Data(hrp, zero + convertBits(firstPart, 8, 5, true)).address,
Bech32Data(hrp, zero + convertBits(secondPart, 8, 5, true)).address,
)
}
/**
* Decodes a Bech32 String
*/
fun decode(bech32: String): Bech32Data {
require(bech32.length in MIN_VALID_LENGTH..MAX_VALID_LENGTH) { "invalid bech32 string length" }
require(bech32.toCharArray()
.none { c -> c.code < MIN_VALID_CODEPOINT || c.code > MAX_VALID_CODEPOINT })
{
"invalid character in bech32: ${
bech32.toCharArray().map { c -> c.code }
.filter { c -> c < MIN_VALID_CODEPOINT || c > MAX_VALID_CODEPOINT }
}"
}
require(bech32 == bech32.lowercase(ROOT) || bech32 == bech32.uppercase(ROOT))
{ "bech32 must be either all upper or lower case" }
require(bech32.substring(1).dropLast(CHECKSUM_SIZE)
.contains('1')) { "invalid index of '1'" }
val hrp = bech32.substringBeforeLast('1').lowercase(ROOT)
val dataString = bech32.substringAfterLast('1').lowercase(ROOT)
require(dataString.toCharArray()
.all { c -> charset.contains(c) }) { "invalid data encoding character in bech32" }
val dataBytes = dataString.map { c -> charset.indexOf(c).toByte() }.toByteArray()
val checkBytes =
dataString.takeLast(CHECKSUM_SIZE).map { c -> charset.indexOf(c).toByte() }
.toByteArray()
val actualSum = checksum(hrp, dataBytes.dropLast(CHECKSUM_SIZE).toTypedArray())
require(1 == polymod(expandHrp(hrp).plus(dataBytes.map { d -> d.toInt() }))) { "checksum failed: $checkBytes != $actualSum" }
return Bech32Data(hrp, dataBytes.dropLast(CHECKSUM_SIZE).toByteArray())
}
/**
* ConvertBits regroups bytes with toBits set based on reading groups of bits as a continuous stream group by fromBits.
* This process is used to convert from base64 (from 8) to base32 (to 5) or the inverse.
*/
fun convertBits(data: ByteArray, fromBits: Int, toBits: Int, pad: Boolean): ByteArray {
require(fromBits in 1..8 && toBits in 1..8) { "only bit groups between 1 and 8 are supported" }
// resulting bytes with each containing the toBits bits from the input set.
val regrouped = arrayListOf<Byte>()
var nextByte = 0.toUByte()
var filledBits = 0
data.forEach { d ->
// discard unused bits.
var b = (d.toUByte() shl (8 - fromBits))
// How many bits remain to extract from input data.
var remainFromBits = fromBits
while (remainFromBits > 0) {
// How many bits remain to be copied in
val remainToBits = toBits - filledBits
// we extract the remaining bits unless that is more than we need.
val toExtract =
remainFromBits.takeUnless { remainToBits < remainFromBits } ?: remainToBits
check(toExtract >= 0) { "extract should be positive" }
// move existing bits to the left to make room for bits toExtract, copy in bits to extract
nextByte = (nextByte shl toExtract) or (b shr (8 - toExtract))
// discard extracted bits and update position counters
b = b shl toExtract
remainFromBits -= toExtract
filledBits += toExtract
// if we have a complete group then reset.
if (filledBits == toBits) {
regrouped.add(nextByte.toByte())
filledBits = 0
nextByte = 0.toUByte()
}
}
}
// pad any unfinished groups as required
if (pad && filledBits > 0) {
nextByte = nextByte shl (toBits - filledBits)
regrouped.add(nextByte.toByte())
filledBits = 0
nextByte = 0.toUByte()
}
return regrouped.toByteArray()
}
/**
* Encodes data 5-bit bytes (data) with a given human readable portion (hrp) into a bech32 string.
* @see convertBits for conversion or ideally use the Bech32Data extension functions
*/
fun encode(hrp: String, fiveBitData: ByteArray): String {
return (fiveBitData.plus(checksum(hrp, fiveBitData.toTypedArray()))
.map { b -> charset[b.toInt()] }).joinToString("", hrp + "1")
}
/**
* Calculates a bech32 checksum based on BIP 173 specification
*/
fun checksum(hrp: String, data: Array<Byte>): ByteArray {
val values = expandHrp(hrp)
.plus(data.map { d -> d.toInt() })
.plus(Array(6) { 0 }.toIntArray())
val poly = polymod(values) xor 1
return (0..5).map {
((poly shr (5 * (5 - it))) and 31).toByte()
}.toByteArray()
}
/**
* Expands the human readable prefix per BIP173 for Checksum encoding
*/
private fun expandHrp(hrp: String) =
hrp.map { c -> c.code shr 5 }
.plus(0)
.plus(hrp.map { c -> c.code and 31 })
.toIntArray()
/**
* Polynomial division function for checksum calculation. For details see BIP173
*/
fun polymod(values: IntArray): Int {
var chk = 1
return values.map { num ->
val b = chk shr 25
chk = ((chk and 0x1ffffff) shl 5) xor num
(0..4).map {
if (((b shr it) and 1) == 1) {
chk = chk xor gen[it]
}
}
}.let { chk }
}
}
}