For Developers/fi2offsets

Background

Canon's firmware update files for the Powershot series cameras are encoded by the manufacturer, the camera rejects unencoded files or files with a wrong encoding. To start the CHDK binary with Canon's firmware update mechanism, the file must be encoded with the correct keys. The automated build process of the Autobuild Server knows the required settings and keys and delivers correct encoded CHDK binaries (ps.fi2 files).

• To create your own CHDK ps.fi2 files (e.g. with the CHDK-Shell), the OPT_FI2 option in /buildconf.inc must be turned on and the file /platform/fi2.inc must hold the keys.

• The keys are not hosted in the SVN, read more about it in this thread: http://chdk.setepontos.com/index.php/topic,2995.0.html

About the keys

The keys can be extracted from a full firmware dump file when the starting offset is known.

To get the keys for a camera, the following things are needed:

1. the fi2 encoding key set (d3, d3enc, d4, d4a, d4b)
2. a full, clean reference firmware dump file
3. the offset where the key starts in the reference firmware dump

• The keys are always 16 bytes long, starting from the offset listed below, written without any delimiter like this sample section:

ifeq ($(KEYSYS), d3)
FI2KEY=112233445566778899AABBCCDDEEFFGG
FI2IV =112233445566778899AABBCCDDEEFFGG
endif

---

Offset table

Developers - pls. fill in the information here...

Camera	Encoding	Reference FW Dump	Offset FI2KEY	Offset FI2IV
G9	d3	G9-100F	0x7E31F0	0x3154D0
SD4000	d4a	SD4000-100D	0x7E366C	0x405130
SX210	d4a	SX210-100C	0x7E3570	0x41522C