Are you planning to publish on ticalc?

Ohhh, that's a really clever use of a calculator (unfortunately not a model I have). I'd love to pull out my TI-84 for 2fa; maybe that'll be a fun project for me

How large does the binary come out to be?

EDIT: I see the 18 KB release now.

I'm not very familiar with programming on the z80 calculators, but I can say some things about this.
You would need to be able to do these on the calculator:
- Take the SHA1 hash for binary data as large as 64 bytes.
- Get the current time
- Read in secret keys from user input
- Store small secret keys in RAM or flash (likely as a variable)
- Display codes on the screen

I imagine that that first one will be the most difficult. You would need to use assembly language (I don't think that there is a C compiler for the Ti84 Plus, and basic is far too slow, although there is a C compiler for the color calculators). I also can't find any implementations of SHA1 in z80 assembly, so you may have to make one on your own.

From what I can remember, the Ti84 has a built in clock, the Ti83 does not. You would need to figure out if there is a particular ROM call that you can use to get the time. If not, maybe it is stored at some memory address.

If after considering all of this, you are still confident that you can write this, then you should read these specifications so you know exactly what it is that you are implementing:
- RFC 2104 HMAC: Keyed-Hashing for Message Authentication
- RFC 4226 HOTP: An HMAC-Based One-Time Password Algorithm
- RFC 6228 TOTP: Time-Based One-Time Password Algorithm
- RFC 4648 The Base16, Base32, and Base64 Data Encodings (Base32 is used to convert user input into binary secret keys)
You could also read the code that I have written, or that of some smartphone authenticator app.

Well, me and beck are currently working on HASHLIB. It's a LibLoad compatible library that does general checksums, CRC, SHA-1, and SHA-256. That's already released, but it was done by me in C and converted to asm... Me and beckadamtheinventor (mostly him -- he's better with assembly) are re-implementing the existing routines in assembly to make them faster and smaller.

https://www.cemetech.net/downloads/files/2123/x2282

We also plan to implement a lightweight version of RSA, using an asymmetric 256-bit keypair. I've already implemented it in a python test server, now it needs to be done calc side so we can test. Essentially, the calculator would create a private key and a public key, and send that to a remote host. The remote host would do the same, sending its own public key back to the initiating calculator. Both local and remote hosts would dump the other host's pubkey into a buffer, and proceed to communicate over this psuedo-RSA framework. I say "pseudo" because RSA needs a minimum of 1024 bits to be considered secure, but this is a calculator after all...

It remains to be seen if we can feasibly pull this off without a great deal of speed-loss in transferring data.

Quote from: Eeems on February 24, 2021, 10:55:35 am

Are you planning to publish on ticalc?

No, sorry. They only have static file uploads and not any links to files. I would like to use github as a single place to upload source an binaries, so that I can make changes in a single place.

Well you can always release major versions on TI-Calc.org. A lot of new people do go to that site.

Hi. I posted to ticalc because everyone said that I should.
https://www.ticalc.org/archives/files/fileinfo/476/47602.html

I know that I misspelled the title of the post. I can update it when I send the new release.