in src/main.rs [148:153]
fn deserialize_signature(sig_bytes: &[u8]) -> Result<(EdwardsPoint, Scalar)> {
let checked_sig_bytes = check_slice_size(sig_bytes, 64, "sig_bytes")?;
let r = deserialize_point(&checked_sig_bytes[..32])?;
let s = deserialize_scalar(&checked_sig_bytes[32..])?;
Ok((r, s))
}