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

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

got the anwser:
in ISO/IEC 7816-4:2013(E), chapter 7.4.3.

Table 10 — Control parameter data objects

Tag | Length | Value | Applies to
'80' Var. Number of data bytes in the file, excluding structural
information Any EF*
'81' Var. Number of data bytes in the file or DO, including structural
information if any File* or DO*

both tag 0x80 and 0x81 can be 4 bytes in length

vincent

2015-05-10 21:57 GMT+02:00 Vincent Le Toux <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
>>
>> Virtual Smart Card Architecture http://vsmartcard.sourceforge.net
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>>
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>
>
> --
> --
> Vincent Le Toux
>
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