Make rand an optional dependency

Cargo.toml

@@ -27,8 +27,9 @@ italian = []
 japanese = []
 korean = []
 spanish = []
+default-langs = ["chinese-simplified", "chinese-traditional", "french", "italian", "japanese", "korean", "spanish"]
 
-default = ["chinese-simplified", "chinese-traditional", "french", "italian", "japanese", "korean", "spanish"]
+default = ["default-langs", "rand"]
 
 [dependencies]
 anyhow = "1.0.57"
@@ -37,7 +38,7 @@ rustc-hash = "1.1.0"
 sha2 = "0.10.2"
 hmac = "0.12.1"
 pbkdf2 = { version = "0.11.0", default-features = false }
-rand = "0.8.5"
+rand = { version = "0.8.5", optional = true }
 once_cell = "1.12.0"
 unicode-normalization = "0.1.19"
 zeroize = { version = "1.5.5", features = ["zeroize_derive"] }

src/crypto.rs

@@ -5,9 +5,9 @@
 //! [Seed]: ../seed/struct.Seed.html
 //!
 
-extern crate rand;
-use self::rand::{thread_rng, RngCore};
 use hmac::Hmac;
+#[cfg(feature = "rand")]
+use rand::{thread_rng, RngCore};
 use sha2::Digest;
 
 const PBKDF2_ROUNDS: u32 = 2048;
@@ -21,6 +21,7 @@ pub(crate) fn sha256_first_byte(input: &[u8]) -> u8 {
 
 /// Random byte generator, used to create new mnemonics
 ///
+#[cfg(feature = "rand")]
 pub(crate) fn gen_random_bytes(byte_length: usize) -> Vec<u8> {
     let mut rng = thread_rng();
     let mut bytes = vec![0u8; byte_length];

src/mnemonic.rs

@@ -1,13 +1,15 @@
-use std::fmt;
-use anyhow::Error;
-use std::mem;
-use unicode_normalization::UnicodeNormalization;
-use zeroize::Zeroizing;
-use crate::crypto::{gen_random_bytes, sha256_first_byte};
+#[cfg(feature = "rand")]
+use crate::crypto::gen_random_bytes;
+use crate::crypto::sha256_first_byte;
 use crate::error::ErrorKind;
 use crate::language::Language;
 use crate::mnemonic_type::MnemonicType;
 use crate::util::{checksum, BitWriter, IterExt};
+use anyhow::Error;
+use std::fmt;
+use std::mem;
+use unicode_normalization::UnicodeNormalization;
+use zeroize::Zeroizing;
 
 /// The primary type in this crate, most tasks require creating or using one.
 ///
@@ -61,6 +63,7 @@ impl Mnemonic {
     ///
     /// [Mnemonic]: ./mnemonic/struct.Mnemonic.html
     /// [Mnemonic::phrase()]: ./mnemonic/struct.Mnemonic.html#method.phrase
+    #[cfg(feature = "rand")]
     pub fn new(mtype: MnemonicType, lang: Language) -> Mnemonic {
         let entropy = gen_random_bytes(mtype.entropy_bits() / 8);
 
@@ -107,12 +110,14 @@ impl Mnemonic {
         //
         // Given the entropy is of correct size, this ought to give us the correct word
         // count.
-        let phrase = Zeroizing::new(entropy
-            .iter()
-            .chain(Some(&checksum_byte))
-            .bits()
-            .map(|bits| wordlist.get_word(bits))
-            .join(" "));
+        let phrase = Zeroizing::new(
+            entropy
+                .iter()
+                .chain(Some(&checksum_byte))
+                .bits()
+                .map(|bits| wordlist.get_word(bits))
+                .join(" "),
+        );
 
         Mnemonic {
             phrase,
@@ -139,10 +144,12 @@ impl Mnemonic {
     ///
     /// [Mnemonic]: ../mnemonic/struct.Mnemonic.html
     pub fn from_phrase(phrase: &str, lang: Language) -> Result<Mnemonic, Error> {
-        let phrase = Zeroizing::new(phrase
-            .split_whitespace()
-            .map(|w| w.nfkd())
-            .join::<String>(" "));
+        let phrase = Zeroizing::new(
+            phrase
+                .split_whitespace()
+                .map(|w| w.nfkd())
+                .join::<String>(" "),
+        );
 
         // this also validates the checksum and phrase length before returning the entropy so we
         // can store it. We don't use the validate function here to avoid having a public API that