Unfortunately the serialised size is likely never going to be the same
as the type's size in memory, as most serialisation formats define
additional headers for parsing safety reasons, such as buffer lengths
and type information.
generic_array v0.12 no longer serializes GenericArray as a Vec,
which reduces the serialized size of PublicKey, Signature, and
SecretKey by 8 bytes. Now that generic_array has been upgraded,
these tests simply ensure the serialization size doesn't change
in the future.
The API for this isn't the greatest and I apologise for that. Suggestions for
improvement welcome. One thing which @hdevalence and I considered was to
change the function signature to:
pub fn verify_batch<D, C, M, S, K>(messages: M,
signatures: S,
public_keys: K,
csprng: &mut C) -> Result<(), SignatureError>
where D: Digest<OutputSize = U64> + Default,
C: Rng + CryptoRng,
M: IntoIterator<Item = &[u8]>,
S: IntoIterator,
S::Item: Borrow<Signature>,
K: IntoIterator,
K::Item: Borrow<Signature>,
The other improvement which could be made is to implement 128-bit scalars for
the randomnesses.
* CLOSES#27
This also simplifies the verification logic. Because the verification check
happens in variable time, we don't need to do a constant-time eq check at the
end, so we can drop the `subtle` dependency entirely.
The `DecodingError` type becomes `SignatureError` and is also used to
signal failing verifications.
This code was significantly based off without boats' error types in
commit 6c1acaca7c, and also upon
conversation with them. Please target them with praise, and blame me
for whatever mistakes I might have made.
Advantages of a custom error type:
- It can be more easily integrated into other error types by clients;
they can implement From<FromBytesError> for their error types, or
they can use a library like failure.
- It is a zero-sized type, which can enable some representational
optimizations.
- It can be easier and more stable to test for.
