Re: [Opensc-devel] iso7816_process_fci: getting the size of the file

[Frank M. <mo...@in...>]

On Sunday, May 10 at 09:18PM, Frank Morgner wrote:
> On Sunday, May 10 at 08:48PM, Vincent Le Toux wrote:
> > Hi,
> > 
> > I've a question about how the file size is retrieved.
> > It is implemented in iso7816.c:
> > https://github.com/OpenSC/OpenSC/blob/master/src/libopensc/iso7816.c#L362-373
> > 
> > I'm not a DER expert that's why I'm asking.
> > 
> > Is a size encoded with the attribute 0x80 with 4 bytes valid ?
> > How can I find the difference between 0x81 & 0x80 ?
> >
> > I get a card with both 0x80 (4 bytes) and 0x81 (2 bytes) tags.
> > If a 4 bytes is valid, I'd like to propose a patch to the iso7816.c file to
> > handle it.
> 
> You most likely are interested in the 0x80 size only. See
> http://www.cardwerk.com/smartcards/smartcard_standard_ISO7816-4_5_basic_organizations.aspx#table2
> 
> Newer versions of ISO 7816-4 define the length of 0x80 to be variable
> and the length of 0x81 to be 2. So your card is conforming to the
> standard though there are cases where the ISO's restriction does not
> make sense.

Update: The newest version of the standard should have both length variable.

-- 
Frank Morgner

Virtual Smart Card Architecture http://vsmartcard.sourceforge.net
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