FIDO1 was mostly just a pile of bytes. Sadly, some silly ASN.1 encoding for signatures was used that treated the big numbers as numbers instead of byte strings,

FIDO1 was mostly just a pile of bytes. Sadly, some silly ASN.1 encoding for signatures was used that treated the big numbers as numbers instead of byte strings, causing a variable length encoding, but this wasn’t a big deal. If you wanted attestation, you had to deal with X.509, but that’s par for the course. Other than that, the spec was delightfully boring.