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rust: select checksum by expanded codeword length #76

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rust: select checksum by expanded codeword length #76

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30 changes: 18 additions & 12 deletions reference/rust-codex32/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,12 +14,12 @@

//! codex32 Reference Implementation
//!
//! This project is a reference implementation of BIP-XXX "codex32", a project
//! This project is a reference implementation of BIP-0093 "codex32", a project
//! by Leon Olson Curr and Pearlwort Snead to produce checksummed and secret-shared
//! BIP32 master seeds.
//!
//! References:
//! * BIP-XXX <https://github.com/apoelstra/bips/blob/2023-02--volvelles/bip-0000.mediawiki>
//! * BIP-0093 <https://github.com/bitcoin/bips/blob/master/bip-0093.mediawiki>
//! * The codex32 website <https://www.secretcodex32.com>
//! * BIP-0173 "bech32" <https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki>
//! * BIP-0032 "BIP 32" <https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki>
Expand Down Expand Up @@ -97,6 +97,13 @@ pub enum Case {
Upper,
}

fn expanded_length(s: &str) -> usize {
match s.rsplit_once('1') {
Some((hrp, data)) => 2 * hrp.len() + 1 + data.len(),
None => 1 + s.len(),
}
}

/// A codex32 string, containing a valid checksum
#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub struct Codex32String(String);
Expand All @@ -120,7 +127,7 @@ impl Codex32String {
/// Construct a codex32 string from a not-yet-checksummed string
pub fn from_unchecksummed_string(mut s: String) -> Result<Self, Error> {
// Determine what checksum to use and extend the string
let (len, mut checksum) = if s.len() < 81 {
let (len, mut checksum) = if expanded_length(&s) < 81 {
(13, checksum::Engine::new_codex32_short())
} else {
(15, checksum::Engine::new_codex32_long())
Expand All @@ -146,9 +153,10 @@ impl Codex32String {

/// Construct a codex32 string from an already-checksummed string
pub fn from_string(s: String) -> Result<Self, Error> {
let (name, mut checksum) = if s.len() >= 48 && s.len() < 94 {
let codeword_length = expanded_length(&s);
let (name, mut checksum) = if s.len() >= 48 && codeword_length < 94 {
("short", checksum::Engine::new_codex32_short())
} else if s.len() >= 125 && s.len() < 128 {
} else if codeword_length >= 96 && s.len() < 128 {
("long", checksum::Engine::new_codex32_long())
} else {
return Err(Error::InvalidLength(s.len()));
Expand Down Expand Up @@ -179,7 +187,7 @@ impl Codex32String {
Some((s1, s2)) => (s1, s2),
None => ("", &self.0[..]),
};
let checksum_len = if self.0.len() > 93 { 15 } else { 13 };
let checksum_len = if expanded_length(&self.0) > 93 { 15 } else { 13 };
let ret = Parts {
hrp,
threshold: match s.as_bytes()[0] {
Expand Down Expand Up @@ -361,7 +369,7 @@ impl Codex32String {
}

// Initialize checksum engine with HRP and header
let mut checksum = if data.len() < 51 {
let mut checksum = if expanded_length(&ret) < 81 {
checksum::Engine::new_codex32_short()
} else {
checksum::Engine::new_codex32_long()
Expand Down Expand Up @@ -605,14 +613,13 @@ mod tests {
let wrong_checksums = [
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxurfvwmdcmymdufv",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxcsyppjkd8lz4hx3",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxu6hwvl5p0l9xf3c",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxwqey9rfs6smenxa",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxv70wkzrjr4ntqet",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx3hmlrmpa4zl0v",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxrfggf88znkaup",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxpt7l4aycv9qzj",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxus27z9xtyxyw3",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxcwm4re8fs78vn",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxr335l5tv88js3",
"ms12fauxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxky0ua3ha84qk8",
];
for chk in wrong_checksums {
let err = Codex32String::from_string(chk.into());
Expand All @@ -632,17 +639,16 @@ mod tests {
#[test]
fn bip_invalid_improper_length() {
let bad_length = [
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxwqey9rfs6smenxa",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxw0a4c70rfefn4",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxk4pavy5n46nea",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxx9lrwar5zwng4w",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxr335l5tv88js3",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxvu7q9nz8p7dj68v",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxpq6k542scdxndq3",
"ms10fauxsxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxkmfw6jm270mz6ej",
"ms12fauxxxxxxxxxxxxxxxxxxxxxxxxxxzhddxw99w7xws",
"ms12fauxxxxxxxxxxxxxxxxxxxxxxxxxxxx42cux6um92rz",
"ms12fauxxxxxxxxxxxxxxxxxxxxxxxxxxxxxarja5kqukdhy9",
"ms12fauxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxky0ua3ha84qk8",
"ms12fauxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx9eheesxadh2n2n9",
"ms12fauxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx9llwmgesfulcj2z",
"ms12fauxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx02ev7caq6n9fgkf",
Expand Down