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use crate::error::ErrorKind; use failure::Error; use std::fmt; const ENTROPY_OFFSET: usize = 8; /// Determines the number of words that will be present in a [`KeyPhrase`][KeyPhrase] phrase /// /// Also directly affects the amount of entropy that will be used to create a [`KeyPhrase`][KeyPhrase], /// and therefore the cryptographic strength of the HD wallet keys/addresses that can be derived from /// it using the [`Seed`][Seed]. /// /// For example, a 12 word keyphrase is essentially a friendly representation of a 128-bit key, /// while a 24 word keyphrase is essentially a 256-bit key. /// /// If you know you want a specific phrase length, you can use the enum variant directly, for example /// `KeyPhraseType::Words12`. /// /// You can also get a `KeyPhraseType` that corresponds to one of the standard BIP39 key sizes by /// passing arbitrary `usize` values: /// /// ``` /// use keyphrase::{KeyPhraseType}; /// /// let keyphrase_type = KeyPhraseType::for_key_size(128).unwrap(); /// ``` /// /// [KeyPhraseType]: ../keyphrase_type/struct.KeyPhraseType.html /// [KeyPhrase]: ../keyphrase/struct.KeyPhrase.html /// [Seed]: ../seed/struct.Seed.html /// #[derive(Debug, Copy, Clone)] pub enum KeyPhraseType { // ... = (entropy_bits << ...) | checksum_bits Words12 = (128 << ENTROPY_OFFSET) | 4, Words15 = (160 << ENTROPY_OFFSET) | 5, Words18 = (192 << ENTROPY_OFFSET) | 6, Words21 = (224 << ENTROPY_OFFSET) | 7, Words24 = (256 << ENTROPY_OFFSET) | 8, } impl KeyPhraseType { /// Get a `KeyPhraseType` for a keyphrase with a specific number of words /// /// Specifying a word count not provided for by the BIP39 standard will return an `Error` /// of kind `ErrorKind::InvalidWordLength`. /// /// # Example /// ``` /// use keyphrase::{KeyPhraseType}; /// /// let keyphrase_type = KeyPhraseType::for_word_count(12).unwrap(); /// ``` pub fn for_word_count(size: usize) -> Result<KeyPhraseType, Error> { let keyphrase_type: KeyPhraseType = match size { 12 => KeyPhraseType::Words12, 15 => KeyPhraseType::Words15, 18 => KeyPhraseType::Words18, 21 => KeyPhraseType::Words21, 24 => KeyPhraseType::Words24, _ => Err(ErrorKind::InvalidWordLength(size))?, }; Ok(keyphrase_type) } /// Get a `KeyPhraseType` for a keyphrase representing the given key size as bits /// /// Specifying a key size not provided for by the BIP39 standard will return an `Error` /// of kind `ErrorKind::InvalidKeysize`. /// /// # Example /// ``` /// use keyphrase::{KeyPhraseType}; /// /// let keyphrase_type = KeyPhraseType::for_key_size(128).unwrap(); /// ``` pub fn for_key_size(size: usize) -> Result<KeyPhraseType, Error> { let keyphrase_type: KeyPhraseType = match size { 128 => KeyPhraseType::Words12, 160 => KeyPhraseType::Words15, 192 => KeyPhraseType::Words18, 224 => KeyPhraseType::Words21, 256 => KeyPhraseType::Words24, _ => Err(ErrorKind::InvalidKeysize(size))?, }; Ok(keyphrase_type) } /// Get a `KeyPhraseType` for an existing keyphrase /// /// This can be used when you need information about a keyphrase based on the number of /// words, for example you can get the entropy value using [`KeyPhraseType::entropy_bits`][KeyPhraseType::entropy_bits()]. /// /// Specifying a phrase that does not match one of the standard BIP39 phrase lengths will return /// an `Error` of kind `ErrorKind::InvalidWordLength`. The phrase will not be validated in any /// other way. /// /// # Example /// ``` /// use keyphrase::{KeyPhraseType}; /// /// let test_keyphrase = "park remain person kitchen mule spell knee armed position rail grid ankle"; /// /// let keyphrase_type = KeyPhraseType::for_phrase(test_keyphrase).unwrap(); /// /// let entropy_bits = keyphrase_type.entropy_bits(); /// ``` /// /// [KeyPhraseType::entropy_bits()]: ./enum.KeyPhraseType.html#method.entropy_bits pub fn for_phrase(phrase: &str) -> Result<KeyPhraseType, Error> { let word_count: usize = phrase.split(" ").count(); Self::for_word_count(word_count) } /// Return the number of entropy+checksum bits /// /// /// # Example /// ``` /// use keyphrase::{KeyPhraseType}; /// /// let test_keyphrase = "park remain person kitchen mule spell knee armed position rail grid ankle"; /// /// let keyphrase_type = KeyPhraseType::for_phrase(test_keyphrase).unwrap(); /// /// let total_bits = keyphrase_type.total_bits(); /// ``` pub fn total_bits(&self) -> usize { self.entropy_bits() + self.checksum_bits() as usize } /// Return the number of entropy bits /// /// /// # Example /// ``` /// use keyphrase::{KeyPhraseType}; /// /// let test_keyphrase = "park remain person kitchen mule spell knee armed position rail grid ankle"; /// /// let keyphrase_type = KeyPhraseType::for_phrase(test_keyphrase).unwrap(); /// /// let entropy_bits = keyphrase_type.entropy_bits(); /// ``` pub fn entropy_bits(&self) -> usize { (*self as usize) >> ENTROPY_OFFSET } /// Return the number of checksum bits /// /// /// # Example /// ``` /// use keyphrase::{KeyPhraseType}; /// /// let test_keyphrase = "park remain person kitchen mule spell knee armed position rail grid ankle"; /// /// let keyphrase_type = KeyPhraseType::for_phrase(test_keyphrase).unwrap(); /// /// let checksum_bits = keyphrase_type.checksum_bits(); /// ``` pub fn checksum_bits(&self) -> u8 { (*self as usize) as u8 } /// Return the number of words /// /// /// # Example /// ``` /// use keyphrase::{KeyPhraseType}; /// /// let keyphrase_type = KeyPhraseType::Words12; /// /// let word_count = keyphrase_type.word_count(); /// ``` pub fn word_count(&self) -> usize { self.total_bits() / 11 } } impl Default for KeyPhraseType { fn default() -> KeyPhraseType { KeyPhraseType::Words12 } } impl fmt::Display for KeyPhraseType { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!( f, "{} words ({}bits)", self.word_count(), self.entropy_bits() ) } } #[cfg(test)] mod test { use super::*; #[test] fn word_count() { assert_eq!(KeyPhraseType::Words12.word_count(), 12); assert_eq!(KeyPhraseType::Words15.word_count(), 15); assert_eq!(KeyPhraseType::Words18.word_count(), 18); assert_eq!(KeyPhraseType::Words21.word_count(), 21); assert_eq!(KeyPhraseType::Words24.word_count(), 24); } #[test] fn entropy_bits() { assert_eq!(KeyPhraseType::Words12.entropy_bits(), 128); assert_eq!(KeyPhraseType::Words15.entropy_bits(), 160); assert_eq!(KeyPhraseType::Words18.entropy_bits(), 192); assert_eq!(KeyPhraseType::Words21.entropy_bits(), 224); assert_eq!(KeyPhraseType::Words24.entropy_bits(), 256); } #[test] fn checksum_bits() { assert_eq!(KeyPhraseType::Words12.checksum_bits(), 4); assert_eq!(KeyPhraseType::Words15.checksum_bits(), 5); assert_eq!(KeyPhraseType::Words18.checksum_bits(), 6); assert_eq!(KeyPhraseType::Words21.checksum_bits(), 7); assert_eq!(KeyPhraseType::Words24.checksum_bits(), 8); } }