Securing your implant - first steps after installation

Disable lock bytes so they cannot be used to lock any memory blocks as read-only

Update the password block with a custom, non-default password value

Update the memory protection option to write-only protection

Update the memory protection range to protect the configuration bytes

The NFC chip inside this product is an NTAG family chip from NXP. This chip type was designed for use in more typical NFC applications such as smart posters, labels, and other disposable use cases where the memory contents would typically be written and then locked so it could not be changed. This is done using built-in “lock bytes” which are OTP (one time programmable). That means that once the lock bytes are turned on to protect memory blocks, they can never be unlocked. Once any memory block is locked, it will forever be read-only, which is not ideal for a chip implant. Also, many common NFC smartphone apps and software applications offer ways to “lock” or “protect” your tag, making it very easy to accidentally lock your xNT as read-only.In addition to lock bytes, the NTAG offers a 32bit password protection function. It can be used to password-protect just writing to or both reading from and writing to the user memory space of the NTAG chip. Regardless of what some NFC smartphone apps indicate, it is not possible to remove or disable the password, it is only possible to set the password to the factory default hexadecimal value of 0xFF 0xFF 0xFF 0xFF. If the password is not changed from the factory default then anyone could easily authenticate, change your password, then write data or change protection options for your chip implant to lock you out of your own chip.Finally, many of the critical configuration bytes used by NTAG chips are stored in the last few pages of the chip’s memory. This means that it may be possible for an NFC application that does not properly detect or honor the memory schema of the chip to accidentally attempt to write NDEF record data (the data you’re trying to store on the chip) overtop of the configuration bytes. For example, if the data you are attempting to write is longer than the memory pages available, the remainder of the data might be written overtop of configuration bytes, which contain settings that are potentially dangerous to modify. Accidentally writing to those memory pages could result in your chip’s configuration being irreversibly locked.To help our customers protect their tag from accidental modification or malicious attack, we have developed Dangerous NFC for Android. Our DNFC app allows customers to secure their tag by doing the following things;This approach allows the entire user memory space to be written to/updated, while at the same time protecting the configuration bytes and password values at the bottom end of the xNT memory space. This means an application cannot accidentally write data unintentionally to any configuration bytes. It also means the password of the xNT cannot be updated without first authenticating. This means you will need the current password in order to update or change the password. Without updating the dynamic memory protection range, it would technically be possible to just write a new password without first knowing the old password.Ultimately, once secured by Dangerous NFC , you are free to use any other NFC app to write data to the tag and not need to be afraid of accidentally locking the tag, or changing the configuration bytes, or someone maliciously locking your tag or changing your password. We suggest using NXP’s TagWriter app.