I have walked through the different fields of x509 certificates and came across some fields which enable to limit the usage of the certificate (for example for certain domains). Is it possible to limit which public key sizes and signature algorithm of the next certificates in the certificate chain are allowed?
These kinds of policies come from the Certificate Practise Statement of the CA signing a request and should not live in the fields of a CA certificate.
- If you don't want e.g. < 3000 bit keys in child certs, the correct approach would be to refuse to sign a request that does not comply with minimums rather than expect the client to interperet a policy encoded in the CA's certificate.
- In contrast, the signature algorithm and hash size are set by the CA when the signature is generated, so this is entirely down to the configuration of the signing process used.