问题
I was able to find a way to protect a tag with a password, the problem is that I don't know how to remove it. According to this datasheet, if you set the value of AUTH0 outside its range, the password will be disabled, I tried doing that but nothing happened.
This is how I am trying to disable the password:
- Open tag
- Authenticate tag
- Set value of AUTH0 (page 41, third byte) to 256 (range of AUTH0 is 0 to 255 according to the datasheet)
- Close tag
回答1:
You indicate that you change AUTH0 on page 41 (0x29). This is the location of the configuration pages for NTAG213. If you have an NTAG216, the configuration pages start at page 227 (0xE3). Hence, AUTH0 is the third byte of page 0xE3.
In order to update the value of AUTH0, the configuration pages must be writable. As you authenticate to the tag, you already make sure that the password-based reversible write protection (or read+write protection) is temporarily disabled. However, there is also the possibility that the configuration pages are permanently write-protected through the configuration lock bit (CFGLCK, 6th bit of the first byte on page 0xE4 (or page 0x2A for NTAG213). If this bit is set to 1, the value of AUTH0 cannot be changed. So you should check this value in order to be sure that updating AUTH0 is even possible on your tag.
Setting a byte value (AUTH0) to anything outside the range 0-255 is simply not possible. A byte value consists of 8 bits and can, therefore, only hold values from 0 to 28-1. If you use something like
(byte) 256then this is eqivalent to(byte) 0. Hence, you most likely set the value to 0 indicating that the whole tag should be password protected. You should actually set AUTH0 to a value past the last page address (i.e. at least 0xE7 for NTAG216, at least 0x2D for NTAG213, or simply 0xFF (255)).
来源：https://stackoverflow.com/questions/34390476/how-to-remove-password-protection-in-ntag216