Nice post, good for a certain degree of "dissecting". I assumed however that we'd be going all the way down to the bytes. I spent quite a long time with "A Lay

Nice post, good for a certain degree of "dissecting". I assumed however that we'd be going all the way down to the bytes. I spent quite a long time with "A Layman's Guide to a Subset of ASN.1, BER, and DER" as a close companion, though it looks like letsencrypt has created a friendlier intro: https://letsencrypt.org/docs/a-warm-welcome-to-asn1-and-der/ https://letsencrypt.org/docs/a-warm-welcome-to-asn1-and-der/ While it's relatively rare that you'll have to understand the encoding, it can be a lifesaver to have that skill if you're looking at some raw dump of of a cert (or other BER/DER encoded data). I had a co-worker once who was famed for having a BER/DER decoder in his head. He'd look at a hex dump and point to a spot somewhere in the middle and declare something like "there's your problem: the cert signing bit isn't set in your key usage extension".