libx509-ocaml-dev 0.16.5-2build11 (arm64 binary) in ubuntu oracular

 X.509 is a public key infrastructure used mostly on the Internet. It
 consists of certificates which include public keys and identifiers,
 signed by an authority. Authorities must be exchanged over a second
 channel to establish the trust relationship. This library implements
 most parts of RFC5280 and RFC6125. The Public Key Cryptography
 Standards (PKCS) defines encoding and decoding (in ASN.1 DER and PEM
 format), which is also implemented by this library - namely PKCS 1,
 PKCS 5, PKCS 7, PKCS 8, PKCS 9, PKCS 10, and PKCS 12.
 .
 This package contains development files.