Revision as of 18:22, 4 January 2020

General Observations

always exactly 107 byte
all binary, there are no recognizable ASCII strings in this
the last ~64 byte have very high entropy, suggesting a signature or a compressed section
there's a base64 encoded sequential number printed below the Aztec code on the ticket, containing 24bit.
there's a 13 digit order number and optionally a 15 digit reference number on each ticket, sequential and covering multiple sections/travelers
one barcode seems to be exactly for one journey section
all available samples are for a single adult traveler

Byte[:Bit] (MSB)	Content	Meaning	Notes
0 - 1	0b0001 0000 0b0000 0010	unknown	fixed in all samples
2	0b1010 0000 or 0b1000 0000	unknown
3	0b0000 0001	unknown	fixed in all samples
4:0 4:6	null
4:7 - 5:7	9 bit day number		day of travel, counted from Jan 1
6 - 12	0x00 0x49 0x24 0x92 0x49 0x24 0x92		fixed in all samples, patterns repeats below
13 - 21	todo	todo
22:0 - 23:5	14 bit uint	train number	might be including too many/few leading 0 bits, 0 for buses
23:6 - 28	todo	todo
29	0b0010 0000		fixed in all samples
30:0 - 30:5	5 bit uint	coach number	leading 0 bits uncertain
30:6 - 31:4	7 bit uint	seat number	0 if no seat reserved
31:5 - 31:7	0b100		fixed in all samples
32 - 40	0x89 0x24 0x92 0x49 0x24 0x90 0x60 0x00 0x01		fixed in all samples, repeats a pattern from 6-12
41:0 - 42:0	todo	todo	varies slightly between samples
42:1 - 106:0	64 byte varying		high entropy in all samples, signature?
106:1 - 106:7	null

@@ Line 31: / Line 31: @@
 | 22:0 - 23:5 || 14 bit uint || train number || might be including too many/few leading 0 bits, 0 for buses
 |-
-| 23:6 - 29 || todo || todo ||
+| 23:6 - 28 || todo || todo ||
+|-
+| 29 || 0b0010 0000 || || fixed in all samples
 |-
 | 30:0 - 30:5 || 5 bit uint || coach number || leading 0 bits uncertain