1+ package fr.acinq.bitcoin
2+
3+ import fr.acinq.bitcoin.DeterministicWallet.derivePrivateKey
4+ import fr.acinq.bitcoin.DeterministicWallet.publicKey
5+ import kotlin.jvm.JvmStatic
6+
7+ public object Descriptor {
8+ private fun polyMod (cc : Long , value : Int ): Long {
9+ var c = cc
10+ val c0 = c shr 35
11+ c = ((c and 0x7ffffffffL ) shl 5 ) xor value.toLong()
12+ if ((c0 and 1L ) != 0L ) c = c xor 0xf5dee51989L
13+ if ((c0 and 2L ) != 0L ) c = c xor 0xa9fdca3312L
14+ if ((c0 and 4L ) != 0L ) c = c xor 0x1bab10e32dL
15+ if ((c0 and 8L ) != 0L ) c = c xor 0x3706b1677aL
16+ if ((c0 and 16L ) != 0L ) c = c xor 0x644d626ffdL
17+ return c
18+ }
19+
20+ @JvmStatic
21+ public fun checksum (span : String ): String {
22+ /* * A character set designed such that:
23+ * - The most common 'unprotected' descriptor characters (hex, keypaths) are in the first group of 32.
24+ * - Case errors cause an offset that's a multiple of 32.
25+ * - As many alphabetic characters are in the same group (while following the above restrictions).
26+ *
27+ * If p(x) gives the position of a character c in this character set, every group of 3 characters
28+ * (a,b,c) is encoded as the 4 symbols (p(a) & 31, p(b) & 31, p(c) & 31, (p(a) / 32) + 3 * (p(b) / 32) + 9 * (p(c) / 32).
29+ * This means that changes that only affect the lower 5 bits of the position, or only the higher 2 bits, will just
30+ * affect a single symbol.
31+ *
32+ * As a result, within-group-of-32 errors count as 1 symbol, as do cross-group errors that don't affect
33+ * the position within the groups.
34+ */
35+ val INPUT_CHARSET = " 0123456789()[],'/*abcdefgh@:$%{}" + " IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~" + " ijklmnopqrstuvwxyzABCDEFGH`#\"\\ "
36+
37+ /* * The character set for the checksum itself (same as bech32). */
38+ val CHECKSUM_CHARSET = " qpzry9x8gf2tvdw0s3jn54khce6mua7l"
39+
40+ var c = 1L
41+ var cls = 0
42+ var clscount = 0
43+ span.forEach { ch ->
44+ val pos = INPUT_CHARSET .indexOf(ch);
45+ if (pos == - 1 ) return " "
46+ c = polyMod(c, pos and 31 ); // Emit a symbol for the position inside the group, for every character.
47+ cls = cls * 3 + (pos shr 5 ); // Accumulate the group numbers
48+ clscount + = 1
49+ if (clscount == 3 ) {
50+ // Emit an extra symbol representing the group numbers, for every 3 characters.
51+ c = polyMod(c, cls)
52+ cls = 0
53+ clscount = 0
54+ }
55+ }
56+ if (clscount > 0 ) c = polyMod(c, cls)
57+ for (j in 0 until 8 ) c = polyMod(c, 0 ) // Shift further to determine the checksum.
58+ c = c xor 1 // Prevent appending zeroes from not affecting the checksum.
59+
60+ val ret = StringBuilder (" "
61+ for (j in 0 until 8 ) {
62+ val pos1 = (c shr (5 * (7 - j))) and 31
63+ val char = CHECKSUM_CHARSET [pos1.toInt()]
64+ ret[j] = char
65+ }
66+ return ret.toString()
67+ }
68+
69+ private fun getBIP84KeyPath (chainHash : ByteVector32 ): Pair <String , Int > = when (chainHash) {
70+ Block .RegtestGenesisBlock .hash, Block .TestnetGenesisBlock .hash -> " 84'/1'/0'/0" DeterministicWallet .tpub
71+ Block .LivenetGenesisBlock .hash -> " 84'/0'/0'/0" DeterministicWallet .xpub
72+ else -> error(" invalid chain hash $chainHash "
73+ }
74+
75+ @JvmStatic
76+ public fun BIP84Descriptors (chainHash : ByteVector32 , master : DeterministicWallet .ExtendedPrivateKey ): Pair <String , String > {
77+ val (keyPath, _) = getBIP84KeyPath(chainHash)
78+ val accountPub = publicKey(derivePrivateKey(master, KeyPath (keyPath)))
79+ val fingerprint = DeterministicWallet .fingerprint(master) and 0xFFFFFFFFL
80+ return BIP84Descriptors (chainHash, fingerprint, accountPub)
81+ }
82+
83+ @JvmStatic
84+ public fun BIP84Descriptors (chainHash : ByteVector32 , fingerprint : Long , accountPub : DeterministicWallet .ExtendedPublicKey ): Pair <String , String > {
85+ val (keyPath, prefix) = getBIP84KeyPath(chainHash)
86+ val accountDesc = " wpkh([${fingerprint.toString(16 )} /$keyPath ]${DeterministicWallet .encode(accountPub, prefix)} /0/*)"
87+ val changeDesc = " wpkh([${fingerprint.toString(16 )} /$keyPath ]${DeterministicWallet .encode(accountPub, prefix)} /1/*)"
88+ return Pair (
89+ " $accountDesc #${checksum(accountDesc)} "
90+ " $changeDesc #${checksum(changeDesc)} "
91+ )
92+ }
93+ }
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