Guide
Short, accurate articles on SSL/TLS certificates, their types, the 47-day rule and the certificate lifecycle.
The 47-day rule: what CA/Browser Forum ballot SC-081v3 says
The schedule that takes certificate lifetimes from 398 to 47 days, who decided it, why, and what to do now.
10 September 20266 min readWhy certificate revocation does not work and how short lifetimes fix it
The limits of CRL and OCSP, what browsers do, and how short-lived certificates take the place of revocation.
8 September 20265 min readdns-01 validation: DNS APIs for wildcards and internal names
How dns-01 works, propagation, split-horizon DNS and delegating _acme-challenge, narrowing API permissions.
6 September 20266 min readHow expensive is an expired certificate? Outages on the public record
Outages at large organisations caused by expired certificates, and what they have in common.
2 September 20265 min readHow to build a certificate inventory: discovery, ownership, records
Where certificates live, how to find them and what to record; with the NIST guide and Certificate Transparency as sources.
31 August 20266 min readWhat is ACME? How automatic certificate renewal works
The RFC 8555 protocol, validation methods, renewal timing and which authorities offer ACME.
24 August 20267 min readCertificate types: DV, OV, EV, wildcard and the rest
Publicly trusted certificates, internal PKI, client certificates, code signing: which is for what?
19 August 20265 min readWhat is an SSL/TLS certificate and how does it work?
What is inside a certificate, why browsers trust it and what happens when it expires: a short, accurate primer.
12 August 20266 min read
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