packet syntax

[Werner Koch]

On Thu, 12 Apr 2018 05:29, edgar at pettijohn-web.com said:

> did a hexdump of the file and the first word is `99' which in binary
> would be `10011001'. I was expecting to encounter `11000110'.  I'm

OpenPGP (RFC-4880) has several ways to encode a packet header.  This
first byte is called the CTB and reads:

  0x10011001 
     !^^^^##-  0x01  = 2 length bytes follow.
     !!------- 0x06  = Public key
     !-------- Clear = Old style CTB
  0x11000110  
     !^^^^^^
     !!------- 0x06 = Public Key
     !-------- Set  = New style CTB

For a new style CTB the length bytes are Hufmann like encoded.  Bit 7 is
always set.  A basic parser can be found in gpgme/src/data-identify.c


Shalom-Salam,

   Werner

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