Adding slow-hash feature

Cargo.toml

@@ -9,6 +9,9 @@ license = "MIT"
 edition = "2018"
 readme = "README.md"
 
+[features]
+slow-hash = ["scrypt"]
+
 [dependencies]
 aead = "0.2.0"
 curve25519-dalek = "2.0.0"
@@ -16,7 +19,7 @@ generic-array = "0.12.3"
 hkdf = "0.8.0"
 hmac = "0.7.1"
 rand_core = "0.5.1"
-scrypt = "0.2.0"
+scrypt = {version = "0.2.0", optional = true}
 sha2 = "0.8"
 thiserror = "1"
 x25519-dalek = "0.6.0"

src/slow_hash.rs

@@ -6,7 +6,6 @@
 use crate::errors::InternalPakeError;
 
 use generic_array::GenericArray;
-use scrypt::{scrypt, ScryptParams};
 use sha2::{Digest, Sha256};
 
 pub trait SlowHash {
@@ -25,15 +24,15 @@ impl SlowHash for NoOpHash {
     }
 }
 
-pub struct Scrypt;
-
-impl SlowHash for Scrypt {
+#[cfg(feature = "slow-hash")]
+impl SlowHash for scrypt::ScryptParams {
     fn hash(
         input: GenericArray<u8, <Sha256 as Digest>::OutputSize>,
     ) -> Result<Vec<u8>, InternalPakeError> {
-        let params = ScryptParams::new(15, 8, 1).unwrap();
+        let params = scrypt::ScryptParams::new(15, 8, 1).unwrap();
         let mut output = [0u8; 32];
-        scrypt(&input, &[], &params, &mut output).map_err(|_| InternalPakeError::SlowHashError)?;
+        scrypt::scrypt(&input, &[], &params, &mut output)
+            .map_err(|_| InternalPakeError::SlowHashError)?;
         Ok(output.to_vec())
     }
 }