fn oprf_key_from_seed()

in src/opaque.rs [1127:1153]

• 27 lines of code
• 1 McCabe index (conditional complexity)

fn oprf_key_from_seed<CS: voprf::CipherSuite>(
    oprf_seed: &Output<CS::Hash>,
    credential_identifier: &[u8],
) -> Result<GenericArray<u8, <CS::Group as Group>::ScalarLen>, ProtocolError>
where
    <CS::Hash as OutputSizeUser>::OutputSize:
        IsLess<U256> + IsLessOrEqual<<CS::Hash as BlockSizeUser>::BlockSize>,
    CS::Hash: Hash,
    <CS::Hash as CoreProxy>::Core: ProxyHash,
    <<CS::Hash as CoreProxy>::Core as BlockSizeUser>::BlockSize: IsLess<U256>,
    Le<<<CS::Hash as CoreProxy>::Core as BlockSizeUser>::BlockSize, U256>: NonZero,
{
    let mut ikm = GenericArray::<_, <CS::Group as Group>::ScalarLen>::default();
    Hkdf::<CS::Hash>::from_prk(oprf_seed)
        .ok()
        .and_then(|hkdf| {
            hkdf.expand_multi_info(&[credential_identifier, STR_OPRF_KEY], &mut ikm)
                .ok()
        })
        .ok_or(InternalError::HkdfError)?;
    Ok(CS::Group::serialize_scalar(
        CS::Group::hash_to_scalar::<CS>(
            &[ikm.as_slice()],
            &GenericArray::from(*STR_OPAQUE_DERIVE_KEY_PAIR),
        )?,
    ))
}