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CLA= 0x7E in APDU command

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trgorce
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CLA= 0x7E in APDU command

Post by trgorce » Tue May 16, 2017 10:31 pm

Our clients want to use CLA= 0x7E in APDU command. However, when I use javax.smartcardio to send an APDU command with CLA = 0x7E, the CLA my Java Card receives is 0x3C. Does this CLA 0x7E have something wrong? I always thought that the problem is caused by this CLA byte. But I can not point out the reason. Hope anyone can help. Thanks a lot.

popmun09
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Re: CLA= 0x7E in APDU command

Post by popmun09 » Wed May 17, 2017 4:50 am

I'm curious. How do you know the CLA bytes that card receive is 0x3C?

trgorce
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Re: CLA= 0x7E in APDU command

Post by trgorce » Wed May 17, 2017 5:17 am

popmun09 wrote:I'm curious. How do you know the CLA bytes that card receive is 0x3C?


I grabbed the data by Bus Hound. Bus Hound is a tool that can fetch the data from USB driver on PC.

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Re: CLA= 0x7E in APDU command

Post by popmun09 » Wed May 17, 2017 5:55 am

Why must your customer use 0x7E as CLA byte? You may try to communicate with them and use CLA=0x80 or 0x00.

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Re: CLA= 0x7E in APDU command

Post by trgorce » Wed May 17, 2017 11:42 pm

popmun09 wrote:Why must your customer use 0x7E as CLA byte? You may try to communicate with them and use CLA=0x80 or 0x00.


Changing CLA to 0x80 or 0x00 can work. But our customer has required the CLA byte, if I want to change it, I need to find the problem and explain to them. Do you know the where is the problem?

popmun09
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Re: CLA= 0x7E in APDU command

Post by popmun09 » Thu May 18, 2017 2:58 am

0x7E isn't a valid CLA.

The CLA value 0x7E is reserved for inter-industry use. CLA=7E contains relevant bits 0111xxxxb, where x can be 0 or 1. It indicate that both secure messaging and command chaining will be used. Maybe javax.smartcardio detects this CLA value and automatically starts a secure messaging session and so CLA is changed to others, I guess.

trgorce
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Re: CLA= 0x7E in APDU command

Post by trgorce » Thu May 18, 2017 10:31 pm

I am greatly appreciated for your useful info. I have contacted our customer and wait for the news. Thanks.

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