Reply To: How to limit negative verification attemps with Ultralight EV 1

[Jorge Sanmiguel]

For anyone interested in this feature, after some trial and error I was able to write the corresponding bits in the tag with the following code:

            ultralightEV1.enablePasswordProtection(true, 0); // Must be called before writing the tries page since it overwrites the corresponding page, enablePasswordProtection will write 00000000 or 10000000 on the corresponding byte if provided with false and true respectively

        ultralightEV1.authenticatePwd(myKey);





        //Write the limit tries byte, must be done after enablePasswordProtection

        int indexNumTries = ultralightEV1.getTotalMemory() - 12; // Index of associated byte

        int pageTries = indexNumTries / 4; // Index of associated page

        byte[] dataPage = ultralightEV1.read(pageTries); // We read the associated page with the value written by enablePasswordProtection

        byte[] finalPage = new byte[4]; // We create the page to write since dataPage has 16 bytes as documented by taplinx

        System.arraycopy(dataPage, 0, finalPage, 0, 4);

        finalPage[0] = (byte)(dataPage[0]|0x07); // The least 3 significant bytes are the number of tries, we are setting a max of 7 invalid tries but any value from 0 to 7 is valid (note that 0 disables the protection)



        ultralightEV1.write(pageTries, finalPage); //Write the page

Do note that any call to enablePasswordProtection will delete the bytes since it uses the most significative bit of the associated byte to signal if read is password protected and, instead of doing the proper byte operations with the current value of the page, the library will simply overwrite the byte value with 00000000 or 10000000, efectivelly disabling the tries protection.

Hopefully this feature will be supported by taplinx in the future but in the meantime this works.

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