Change the size of key material in SKF to 32 bytes

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `SecretKey` and `SecretKeyFactory` no longer implement `SerializableToArray`, but implement `SerializableToSecretArray` instead. Correspondingly, in the bindings these objects implement `to_secret_bytes()` instead of `__bytes__()` (for Python), and `toSecretBytes()` instead of `toBytes()` (for WASM). ([#53])
 - `SecretKey`, `SecretKeyFactory` and `Signer` do not implement `PartialEq` anymore. Corresponding methods in the bindings were removed as well. ([#53])
 - Bumped `k256` to `0.9` and `ecdsa` to `0.12.2`. ([#53])
+- Reduced the size of key material in `SecretKeyFactory` from 64 to 32 bytes. ([#64])
 
 
 ### Added

umbral-pre/src/keys.rs

@@ -266,7 +266,7 @@ impl fmt::Display for SecretKeyFactoryError {
     }
 }
 
-type SecretKeyFactorySeedSize = U64; // the size of the seed material for key derivation
+type SecretKeyFactorySeedSize = U32; // the size of the seed material for key derivation
 type SecretKeyFactoryDerivedSize = U64; // the size of the derived key (before hashing to scalar)
 type SecretKeyFactorySeed = GenericArray<u8, SecretKeyFactorySeedSize>;