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

[Vincent Le T. <vin...@my...>]

Hi Frank

Can you indicate to me in which chapter for iso 7816-4 the variable 0x80
encoding size is defined ?
I have the ISO/IEC 7816-4:2013 version.

Thanks in advance

regards,
Vincent

2015-05-10 21:18 GMT+02:00 Frank Morgner <mo...@in...>:

> 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.
>
> --
> Frank Morgner
>
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Vincent Le Toux

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