What's Inside a TLS Certificate? X.509, SAN, Chain of Trust and File Formats
A TLS certificate is an X.509 document, signed by a CA, that binds a public key to the names in its SAN list; the client trusts it because the chain of signatures reaches a root in its trust store. With real runs we read the fields with openssl and .NET's X509CertificateLoader, and see the one-level limit of wildcards, Let's Encrypt's cross-signed Generation Y chain, and how a missing intermediate breaks curl but is hidden in .NET by AIA.
14 Nov 2026
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16 min
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3
