project idea: portable password safe

Felix sucotronic at
Thu Sep 12 04:46:29 EDT 2013

Just one more option to take in account for communications with pwsafe. I
remember[1] to some one direction communication (pc to mcu) using blinking
squares on a pc monitor (of course you can also use a mobile phone) and
ldr; it could be used to send info to pwsafe, and then confirm correctness
of data on device.
I've done a jsfiddle to show how it would be to send data to device[2].
Note that there's only a "101" as start sequence (1 means black, 0 white).
And you detect the end of sending when 8x(timeout between bits) has passed
with all blank.


On Wed, Sep 11, 2013 at 5:52 PM, Werner Almesberger
<werner at>wrote:

> EdorFaus wrote:
> > Or, alternately, the device could behave as if the write lock was
> > off, except that all reads/writes goes to a separate jailed section
> Kinda like the journal in a journaling file system ? Yes, that
> could be a possibility: collect all changes, then present the
> user with a "diff" and ask whether to "commit".
> Not sure if that would be convenient with a relatively small
> display, though.
> I'd envision basically the following USB protocols:
> - plain HID
> - feedback over HID (via "features"):
>   - select account entry
>   - password store management
> - USB storage:
>   - read-only mode (access to the ecrypted memory card; that would
>     give you a slow (Full Speed only)  but "trusted" reader)
>   - read-write mode
> - DFU to the internal Flash (for development)
> Not sure whether regular firmware upgrades should also be allowed
> via DFU. In any case, they could come from the memory card.
> - Werner
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