maybe my question would be lost in the forum, but has somebody work with RFID tags? I know I can read them, but can I write or modify the inside data? Does anyone know where can I find more about this?
RFID Standards:
125 Khz (low-frequency) tags are write-once/read-many, and usually only contain a small (permanent) unique identification number.
13.56 Mhz (high-frequency) tags are usually read/write, they can typically store about 1 to 2 kilbytes of data in addition to their preset (permanent) unique ID number.
860-960 Mhz (ultra-high-frequency) tags are typically read/write and can have much larger information storage capacity (I think that 64 KB is the highest currently available for passive tags) in addition to their preset (permanent) unique ID number.
More Information
Most read/write tags can be locked to prevent further writing to specific data-blocks in the tag's internal memory, while leaving other blocks unlocked. Different tag manufacturers make their tags differently, though.
Depending on your intended application, you might have to program your own microcontroller to interface with an embedded RFID read/write module using a manufacturer-specific protocol. That's certainly a lot cheaper than buying a complete RFID read/write unit, as they can cost several thousand dollars. With a custom solution, you can build you own unit that does specifically what you want for as little as $200.
Links
SkyTek - RFID reader manufacturing company (you can buy their products through third-party retailers & wholesalers like Mouser)
Trossen Robotics - You can buy RFID tags and readers (125 Khz & 13.56 Mhz) from here, among other things
I did some development with Mifare Classic (ISO 14443A) cards about 7-8 years ago. You can read and write to all sectors of the card, IIRC the only data you can't change is the serial number. Back then we used a proprietary library from Philips Semiconductors. The command interface to the card was quite alike the ISO 7816-4 (used with standard Smart Cards).
I'd recomment that you look at the OpenPCD platform if you are into development.
This is also of interest regarding the cryptographic functions in some RFID cards.
Some RFID chips are read-write, the majority are read-only. You can find out if your chip is read-only by checking the datasheet.
It depends on the type of chip you are using, but nowerdays most chips you can write. It also depends on how much power you give your RFID device. To read you dont need allot of power and very little line of sight. To right you need them full insight and longer insight
RFID tag has more standards. I have developed the RFID tag on Mifare card (ISO 14443A,B) and ISO 15693. Both of them, you can read/write or modify the data in the block data of RFID tag.
We have recently started looking into RFID solutions at my work place and we found a cheap solution for testing purposes.
One of the units from here:
http://www.sdid.com/products.shtml
Plugs into any windows mobile device with an SD slot and allows reading / writing. There is also a development kit to get you on your way with your own apps.
Hope this helps
来源：https://stackoverflow.com/questions/501302/can-i-write-or-modify-data-on-an-rfid-tag