fn get_password_derived_key()

in src/opaque.rs [1098:1125]

• 26 lines of code
• 2 McCabe index (conditional complexity)

fn get_password_derived_key<CS: CipherSuite>(
    input: &[u8],
    oprf_client: voprf::NonVerifiableClient<CS::OprfGroup>,
    evaluation_element: voprf::EvaluationElement<CS::OprfGroup>,
    slow_hash: Option<&CS::SlowHash>,
) -> Result<(Output<OprfHash<CS>>, Hkdf<OprfHash<CS>>), ProtocolError>
where
    <OprfHash<CS> as OutputSizeUser>::OutputSize:
        IsLess<U256> + IsLessOrEqual<<OprfHash<CS> as BlockSizeUser>::BlockSize>,
    OprfHash<CS>: Hash,
    <OprfHash<CS> as CoreProxy>::Core: ProxyHash,
    <<OprfHash<CS> as CoreProxy>::Core as BlockSizeUser>::BlockSize: IsLess<U256>,
    Le<<<OprfHash<CS> as CoreProxy>::Core as BlockSizeUser>::BlockSize, U256>: NonZero,
{
    let oprf_output = oprf_client.finalize(input, &evaluation_element, None)?;

    let hardened_output = if let Some(slow_hash) = slow_hash {
        slow_hash.hash(oprf_output.clone())
    } else {
        CS::SlowHash::default().hash(oprf_output.clone())
    }
    .map_err(ProtocolError::from)?;

    let mut hkdf = HkdfExtract::<OprfHash<CS>>::new(None);
    hkdf.input_ikm(&oprf_output);
    hkdf.input_ikm(&hardened_output);
    Ok(hkdf.finalize())
}