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List:       ms-smartcardddk
Subject:    Re: CRC calculation by smclib on T=1
From:       Mats Hansson <mats.hansson () INTERTEX ! SE>
Date:       2002-03-08 7:47:57
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I don't know anything of the algorithm's, maybe someone else can enlight you
on that, if it isn't obvious from the ISO 3309 spec.
By "it wouldn't be...." I simply mean this: Both the smartcard and the host
must agree on the same method of calculating the CRC sum. Or more precisely:
for a certain Prologue/Information field in a T=1 packet, both the smartcard
OS and the host (in this case represented by smclib) must end up with
exactly the same result of the calculations. Otherwise, smclib will always
complain about a T=1 packet's CRC, sent from the smartcard, and vice versa.

So if the ISO 3309 leaves lots of room for different interpretations, I
think we are in big trouble, since the smartcard spec. ISO 7816-3 does not
specify the CRC method in detail.

/Mats Hansson


At 16:39 2002-03-07 +0100, you wrote:
>Do you know the algorithm use by card T=1 to compute CRC (I want to know the
>Init value to compute CRC, polynom, and final value insert in the frame send
>by the card)
>what do you mean by "it wouldn't be compatible at all with T=1 cards using
>CRC"?
>Regards
>
>-----Original Message-----
>From: Mats Hansson [mailto:mats.hansson@INTERTEX.SE]
>Sent: jeudi 7 mars 2002 15:55
>To: SmartCardDDK@DISCUSS.MICROSOFT.COM
>Subject: Re: CRC calculation by smclib on T=1
>
>
>Since the ISO 7816-3 standard specifically refers to ISO 3309 (clause 9.4.4)
>I reckon that smclib must use the same method, otherwise it wouldn't be
>compatible at all with T=1 cards using CRC. But I haven't checked. Cards
>using CRC-check seem to be very rare.
>Mats Hansson
>
>At 15:24 2002-03-07 +0100, you wrote:
>>Hi Everyone,
>>Does anybody know how the CRC is computed by smclib when protocol T=1 and
>>EDC=CRC is
>>selected. I think that the polynom use is X^16 + X^12 + X^5 + 1 (ISO 3309)
>>Regards.
>>

Mats Hansson
Intertex Data AB
Rissneleden 45
174 44 Sundbyberg
Sweden

Tel +46-8-6282828    Fax +46-8-6286414    www: http://www.intertex.se

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