I was talking with Pavel (aka PenguinOfDoom, on #twisted) last week about iButtons, and mentioned the JavaButton I picked up years ago that I haven't really managed to do anything with yet. That prompted me to poke around the web site (was dalsemi.com, since bought by http://www.maxim-ic.com), and it turns out they have a new-ish version of the portable C code that interfaces with the things. The last time I looked (version 300b2), there was a single function left unimplemented which prevented the use of JavaButtons on a USB adapter under linux. (non-java buttons were ok, serial port adapters were ok, it was just the combination that didn't work). I don't yet know if that's been fixed in the "new" (2004) version 300 library.

Trying to buy a JavaButton looks hard, much harder than it was when I got mine. It probably requires talking to a sales rep. I got a starter kit that included a DS1957 on a USB key fob, very nicely designed. The only part I can see listed on their web site is the DS1955, which has like 8kB of ram (the DS1957 has more like 150kB). The JavaButtons include cryptographic code, so they require a license/export agreement, but it would have been nice if they made it clear how you obtain such a thing.

Anyway, here are a handful of links, since their web site seems particularly hard to navigate.


list of iButton data sheets
regular ICs (not in a steel can) using the same protocol, usually TO-92
might be the entry point to buying a JavaButton, or maybe just one of their crypto iButtons

UPDATE: no, version 300 still does not support JavaButtons over USB. The specific issue is that JavaButtons require a strong pullup to provide lots of power while they're crunching away in the crypto routines. The USB adapter can do this, but the Linux interface code doesn't know how to turn it on. lib/general/Link/USB_Linux/usblnk.c has a routine named hasPowerDelivery, which currently reads:

SMALLINT hasPowerDelivery(int portnum)
   // Adapter supports it but not implemented yet
   return FALSE;