make `rand` crate optional

Cargo.toml

@@ -26,10 +26,14 @@ default = []
 
 [dev-dependencies]
 serde_json = "1.0"
+rand = "0.3"
 
 [dependencies]
-rand = "0.3"
 libc = "0.2"
 rustc-serialize = "0.3"
 serde = "1.0"
 
+[dependencies.rand]
+version = "0.3"
+optional = true
+

src/key.rs

@@ -16,7 +16,7 @@
 //! # Public and secret keys
 
 use std::marker;
-use rand::Rng;
+#[cfg(any(test, feature = "rand"))] use rand::Rng;
 use serialize::{Decoder, Decodable, Encoder, Encodable};
 use serde::{Serialize, Deserialize, Serializer, Deserializer};
 
@@ -54,6 +54,7 @@ pub const ONE_KEY: SecretKey = SecretKey([0, 0, 0, 0, 0, 0, 0, 0,
 pub struct PublicKey(ffi::PublicKey);
 
 
+#[cfg(any(test, feature = "rand"))]
 fn random_32_bytes<R: Rng>(rng: &mut R) -> [u8; 32] {
     let mut ret = [0u8; 32];
     rng.fill_bytes(&mut ret);
@@ -63,6 +64,7 @@ fn random_32_bytes<R: Rng>(rng: &mut R) -> [u8; 32] {
 impl SecretKey {
     /// Creates a new random secret key
     #[inline]
+    #[cfg(any(test, feature = "rand"))]
     pub fn new<R: Rng>(secp: &Secp256k1, rng: &mut R) -> SecretKey {
         let mut data = random_32_bytes(rng);
         unsafe {

src/lib.rs

@@ -39,16 +39,16 @@
 #![cfg_attr(all(test, feature = "unstable"), feature(test))]
 #[cfg(all(test, feature = "unstable"))] extern crate test;
 #[cfg(test)] extern crate serde_json as json;
+#[cfg(any(test, feature = "rand"))] extern crate rand;
 
 extern crate rustc_serialize as serialize;
 extern crate serde;
 
 extern crate libc;
-extern crate rand;
 
 use libc::size_t;
 use std::{error, fmt, ops, ptr};
-use rand::Rng;
+#[cfg(any(test, feature = "rand"))] use rand::Rng;
 
 #[macro_use]
 mod macros;
@@ -519,6 +519,7 @@ impl Secp256k1 {
 
     /// (Re)randomizes the Secp256k1 context for cheap sidechannel resistence;
     /// see comment in libsecp256k1 commit d2275795f by Gregory Maxwell
+    #[cfg(any(test, feature = "rand"))]
     pub fn randomize<R: Rng>(&mut self, rng: &mut R) {
         let mut seed = [0; 32];
         rng.fill_bytes(&mut seed);
@@ -540,6 +541,7 @@ impl Secp256k1 {
     /// and `key::PublicKey::from_secret_key`; call those functions directly for
     /// batch key generation. Requires a signing-capable context.
     #[inline]
+    #[cfg(any(test, feature = "rand"))]
     pub fn generate_keypair<R: Rng>(&self, rng: &mut R)
                                    -> Result<(key::SecretKey, key::PublicKey), Error> {
         let sk = key::SecretKey::new(self, rng);