OpenPGP packet headers.
Decades ago, when OpenPGP was conceived, saving even a few bits was considered important. As such, OpenPGP uses very compact encodings. The encoding schemes have evolved so that there are now two families: the so-called old format, and new format encodings.
A CTB using the new format encoding.
A CTB using the old format encoding.
A packet's header.
A packet's size.
The CTB variants.
The length encoded for an old style CTB.