Greetings! I’m trying to store all my passwords and 2FA codes on an implant to keep sensitive info off my phone entirely. The 2FA side is mostly sorted as I’m looking at the VivoKey Apex Flex Narrow for that. My question is around password storage. Is it possible to write notes to the Apex, encrypted or even plaintext? I’m not too worried about plaintext given how limited the scan range is. I do have a NExT v2 but the storage is too tight to properly label each entry. I’d love to keep everything on one chip for comfort and simplicity rather than adding a DESFire just for passwords, especially since the Apex already has decent EEPROM available. Has anyone got a notes or password storage solution working on the Apex alongside 2FA? Would love to hear real world experience, Thank you! 
Storing string data like passwords is “expensive” when it comes to memory use. You would be much better off exploring encrypted password management like KeePassXC with HMAC and use the HMAC applet for Apex to decrypt.
If you really wanted to store the data directly on your Apex, the a 16kb or 32kb NDEF container could be used and you just store raw text data.. but indexing and updating the data is not efficient.. you’d have to effectively re-write every page after a change in memory. Encryption / decryption would need to be done on the client side anyway.
Thanks for the info! I think I’m going to go with the raw NDEF container approach. To work around the rewriting limitation I’m planning to do weekly updates; copying everything off, adding new passwords, then writing it all back in one go. Could you point me in the right direction for actually writing raw text to the NDEF container? I’m assuming it’s not as simple as NFC Tools like on a NExT given how the Apex handles it’s memory. Also would applets and the NDEF container share memory or are they allocated separately? I want to make sure running applets alongside it wouldn’t cause any issues as I would need to run the 2FA one! Thanks!
yeah this is going to require some more serious software development to get it working.. ever try claude code?
They share memory yes but it’s more like a hard drive where NDEF is one file and other applets have their own files.. the memory of one doesn’t “bleed” into memory of the other.. but they both use up shared eeprom.
Not specifically Claude but I have used AI to assist with coding before.
Were you thinking of a script that would allow me to access the NDEF? I have coded before but I haven’t done anything super advanced. I did think of writing an applet that works as a plaintext notepad but im guessing that would be a lot more work 
.
Also wondering if it would just make more sense to install a larger DESFire chip alongside the Apex for password storage, keeping the Apex purely for 2FA and security applets. Would that be a simpler solution overall or is the NDEF route still worth pursuing?
how you access the ndef container is up to you.. it depends entirely on your use cases and what makes the most sense for the environment in question. my only reason i thought “ndef” was the advantage of using ndef means accessing the data is standardized.. as long as it’s properly formatted.
that depends on how you want to store data on the DESFire. the most common use of desfire, at least in this community, is to just create an ndef container on it.. so you’re back to working with ndef as a storage “container”. you can just as easily create a custom “file” on the desfire (there are many types of “files” the desfire supports).. the ndef “file” on a desfire is just a generic data storage container but has a standardized AID (application identifier) and the data inside must be ndef formatted.. but using ndef over a generic data container with a custom AID is that ndef comes with the advantage of being standardized.
overall i get the sense that you may have waded into this pool thinking it was a 3ft shallow, only to find it’s 11ft deep. there’s a lot to learn before you can achieve your goal. if you’re in this to learn a lot before you actually get to the point you’re storing passwords on your chip and using it as a real solution, that’s fine.. start with the DESFire datasheet.. learn about NDEF data formats and standards.. but if you only have the energy to tinker or dabble a little bit, go the keepassxc route.
I definitely feel a bit out of my league here. I’m really just looking for a practical way to carry all of my login information with me at all times. My thought was to use the Apex purely for 2FA and security applets, and use a DESFire chip to store encrypted plaintext credentials. I know there are more sophisticated ways to structure data on a DESFire, but I’m not necessarily trying to build a custom smartcard application from scratch. I’m mostly trying to balance practicality with the amount of time and energy I realistically have to invest in learning all of this. The idea originally was to carry everything I need to access my accounts with me in a way that I could not be separated from it even if I were to loose my phone or physical paper backups of my passwords. Does the “xDF3 DESFire EV3 8kB NFC” come pre formatted in a way where for instance; a nearly 8kb plaintext record could be written to it? Sorry if I come across as dismissive, I’m still wrapping my head around how all of this works 
not at all
unfortunately you are going to have to build a custom solution from scratch.. even if you can skip building a smartcard application by just using NDEF applet (NFC Sharing on Apex) for storage. you’ll need to develop an application that will be able to write data to your smartcard storage as well as read it and parse it so it makes sense. if you use the ndef container (nfc sharing) then at least you can then lean on standard NFC libraries to do the basic reading and writing of data from / to the chip so you can focus on data parsing, user interface, etc.
I am with Amal on this
Check out my post here
At the bottom of that and this post you will see a quick demo which will give you an idea of how fast and easy it is to use
Got it, thanks again for all the info! I think I’m going to order some DESFire EV3 8K tags and mess around with them externally first before I think about putting one in my body. I’ll probably see if Claude Code can help me build something that actually works with them too. The idea of having cold password storage in my body is too appealing lol!
It absolutely looks practical and I’ll probably use it as a stopgap while I tinker with some external DESFire chips. I just wish the data was stored on the actual Apex itself and not just the encryption keys.
well, if you get something working with the desfire chips, might as well use an NDEF defined application ID and file type.. then you could just deploy the NFC Sharing applet to your Apex and it will work exactly the same way.
Do you use an iPhone?
If so, there is a solution
Here is the Information
Here is the link to the app
If you are on Android, the app has not been made yet, BUT you can vote to motivate @N0AGI to build an Android version