bip39/
mnemonic_type.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
use crate::error::ErrorKind;
use std::fmt;

const ENTROPY_OFFSET: usize = 8;

/// Determines the number of words that will be present in a [`Mnemonic`][Mnemonic] phrase
///
/// Also directly affects the amount of entropy that will be used to create a [`Mnemonic`][Mnemonic],
/// 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 mnemonic phrase is essentially a friendly representation of a 128-bit key,
/// while a 24 word mnemonic phrase is essentially a 256-bit key.
///
/// If you know you want a specific phrase length, you can use the enum variant directly, for example
/// `MnemonicType::Words12`.
///
/// You can also get a `MnemonicType` that corresponds to one of the standard BIP39 key sizes by
/// passing arbitrary `usize` values:
///
/// ```
/// use bip39::{MnemonicType};
///
/// let mnemonic_type = MnemonicType::for_key_size(128).unwrap();
/// ```
///
/// [MnemonicType]: ../mnemonic_type/struct.MnemonicType.html
/// [Mnemonic]: ../mnemonic/struct.Mnemonic.html
/// [Seed]: ../seed/struct.Seed.html
///
#[derive(Debug, Copy, Clone, Default)]
pub enum MnemonicType {
    //  ... = (entropy_bits << ...)   | checksum_bits
    #[default]
    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 MnemonicType {
    /// Get a `MnemonicType` for a mnemonic phrase 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 bip39::{MnemonicType};
    ///
    /// let mnemonic_type = MnemonicType::for_word_count(12).unwrap();
    /// ```
    pub fn for_word_count(size: usize) -> Result<MnemonicType, ErrorKind> {
        let mnemonic_type = match size {
            12 => MnemonicType::Words12,
            15 => MnemonicType::Words15,
            18 => MnemonicType::Words18,
            21 => MnemonicType::Words21,
            24 => MnemonicType::Words24,
            _ => Err(ErrorKind::InvalidWordLength(size))?,
        };

        Ok(mnemonic_type)
    }

    /// Get a `MnemonicType` for a mnemonic phrase 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 bip39::{MnemonicType};
    ///
    /// let mnemonic_type = MnemonicType::for_key_size(128).unwrap();
    /// ```
    pub fn for_key_size(size: usize) -> Result<MnemonicType, ErrorKind> {
        let mnemonic_type = match size {
            128 => MnemonicType::Words12,
            160 => MnemonicType::Words15,
            192 => MnemonicType::Words18,
            224 => MnemonicType::Words21,
            256 => MnemonicType::Words24,
            _ => Err(ErrorKind::InvalidKeysize(size))?,
        };

        Ok(mnemonic_type)
    }

    /// Get a `MnemonicType` for an existing mnemonic phrase
    ///
    /// This can be used when you need information about a mnemonic phrase based on the number of
    /// words, for example you can get the entropy value using [`MnemonicType::entropy_bits`][MnemonicType::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 bip39::{MnemonicType};
    ///
    /// let test_mnemonic = "park remain person kitchen mule spell knee armed position rail grid ankle";
    ///
    /// let mnemonic_type = MnemonicType::for_phrase(test_mnemonic).unwrap();
    ///
    /// let entropy_bits = mnemonic_type.entropy_bits();
    /// ```
    ///
    /// [MnemonicType::entropy_bits()]: ./enum.MnemonicType.html#method.entropy_bits
    pub fn for_phrase(phrase: &str) -> Result<MnemonicType, ErrorKind> {
        let word_count = phrase.split(' ').count();

        Self::for_word_count(word_count)
    }

    /// Return the number of entropy+checksum bits
    ///
    ///
    /// # Example
    /// ```
    /// use bip39::{MnemonicType};
    ///
    /// let test_mnemonic = "park remain person kitchen mule spell knee armed position rail grid ankle";
    ///
    /// let mnemonic_type = MnemonicType::for_phrase(test_mnemonic).unwrap();
    ///
    /// let total_bits = mnemonic_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 bip39::{MnemonicType};
    ///
    /// let test_mnemonic = "park remain person kitchen mule spell knee armed position rail grid ankle";
    ///
    /// let mnemonic_type = MnemonicType::for_phrase(test_mnemonic).unwrap();
    ///
    /// let entropy_bits = mnemonic_type.entropy_bits();
    /// ```
    pub fn entropy_bits(&self) -> usize {
        (*self as usize) >> ENTROPY_OFFSET
    }

    /// Return the number of checksum bits
    ///
    ///
    /// # Example
    /// ```
    /// use bip39::{MnemonicType};
    ///
    /// let test_mnemonic = "park remain person kitchen mule spell knee armed position rail grid ankle";
    ///
    /// let mnemonic_type = MnemonicType::for_phrase(test_mnemonic).unwrap();
    ///
    /// let checksum_bits = mnemonic_type.checksum_bits();
    /// ```
    pub fn checksum_bits(&self) -> u8 {
        (*self as usize) as u8
    }

    /// Return the number of words
    ///
    ///
    /// # Example
    /// ```
    /// use bip39::{MnemonicType};
    ///
    /// let mnemonic_type = MnemonicType::Words12;
    ///
    /// let word_count = mnemonic_type.word_count();
    /// ```
    pub fn word_count(&self) -> usize {
        self.total_bits() / 11
    }
}

impl fmt::Display for MnemonicType {
    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::*;
    #[cfg(target_arch = "wasm32")]
    use wasm_bindgen_test::*;

    #[cfg_attr(all(target_arch = "wasm32"), wasm_bindgen_test)]
    #[cfg_attr(not(target_arch = "wasm32"), test)]
    fn word_count() {
        assert_eq!(MnemonicType::Words12.word_count(), 12);
        assert_eq!(MnemonicType::Words15.word_count(), 15);
        assert_eq!(MnemonicType::Words18.word_count(), 18);
        assert_eq!(MnemonicType::Words21.word_count(), 21);
        assert_eq!(MnemonicType::Words24.word_count(), 24);
    }

    #[cfg_attr(all(target_arch = "wasm32"), wasm_bindgen_test)]
    #[cfg_attr(not(target_arch = "wasm32"), test)]
    fn entropy_bits() {
        assert_eq!(MnemonicType::Words12.entropy_bits(), 128);
        assert_eq!(MnemonicType::Words15.entropy_bits(), 160);
        assert_eq!(MnemonicType::Words18.entropy_bits(), 192);
        assert_eq!(MnemonicType::Words21.entropy_bits(), 224);
        assert_eq!(MnemonicType::Words24.entropy_bits(), 256);
    }

    #[cfg_attr(all(target_arch = "wasm32"), wasm_bindgen_test)]
    #[cfg_attr(not(target_arch = "wasm32"), test)]
    fn checksum_bits() {
        assert_eq!(MnemonicType::Words12.checksum_bits(), 4);
        assert_eq!(MnemonicType::Words15.checksum_bits(), 5);
        assert_eq!(MnemonicType::Words18.checksum_bits(), 6);
        assert_eq!(MnemonicType::Words21.checksum_bits(), 7);
        assert_eq!(MnemonicType::Words24.checksum_bits(), 8);
    }
}