keyfork-mnemonic-util: Mnemonic::seed(&self) -> Vec<u8>

keyfork-mnemonic-util/src/lib.rs

@@ -197,6 +197,26 @@ impl Mnemonic {
         Ok(Mnemonic { words, wordlist })
     }
 
+    #[must_use]
+    pub fn seed(&self) -> Vec<u8> {
+        let mut bits = vec![false; self.words.len() * 11];
+        for (index, word) in self.words.iter().enumerate() {
+            for bit in 0..11 {
+                bits[index * 11 + bit] = (word & (1 << (10 - bit))) > 0;
+            }
+        }
+        bits.truncate(bits.len() - bits.len() % 32);
+        bits.chunks_exact(8)
+            .map(|chunk| {
+                let mut num = 0u8;
+                for i in 0..8 {
+                    num += u8::from(chunk[7 - i]) << i;
+                }
+                num
+            })
+        .collect::<Vec<_>>()
+    }
+
     #[must_use]
     pub fn into_inner(self) -> (Vec<usize>, Arc<Wordlist>) {
         (self.words, self.wordlist)
@@ -219,6 +239,17 @@ mod tests {
         );
     }
 
+    #[test]
+    fn reproduces_its_own_seed() {
+        let mut random_handle = File::open("/dev/random").unwrap();
+        let entropy = &mut [0u8; 256 / 8];
+        random_handle.read_exact(&mut entropy[..]).unwrap();
+        let wordlist = Wordlist::default().arc();
+        let mnemonic = super::Mnemonic::from_entropy(&entropy[..256 / 8], wordlist).unwrap();
+        let seed = mnemonic.seed();
+        assert_eq!(&seed, entropy);
+    }
+
     #[test]
     fn conforms_to_trezor_tests() {
         let content = include_str!("data/vectors.json");