There is now a branch with experimental authenticated encryption support.

There is no firmware image available yet, so you will need to build the branch from source if you want to try this. Please don't use this if you have any valuable information on the device as it is still very experimental and total loss of data is very likely to occur.

I'm making this available now because it will require significant testing and auditing in order to be useful to most users. If you run into any issues or find problems in the code please let me know.

A quick explanation of how it works:

In order to enable encryption, press CTRL-P and enter a password or passphrase.

The device generates a random salt and stores it in FRAM. It appends the salt to your chosen password and then hashes them using SHA256. The result is the encryption key.

Blaustahl then encrypts the current FRAM contents using ChaCha20-Poly1305 and stores the metadata (nonce and authentication tag) and encrypted data in FRAM.

While encryption is enabled, the device uses buffered mode, in which all editing takes place in an SRAM buffer, that can be encrypted and written to FRAM by pressing CTRL-W.

Each time data is written, the nonce is incremented and the authentication tag is updated.

When you remove the device and plug it back in, you will need to press CTRL-P in order to enter your password, before you're able to view or edit text.

It is possible to disable encryption after entering a valid password by using the command line interface (CTRL-C):

Blaustahl> disable_encryption

This causes Blaustahl to disable encryption and write the plaintext to FRAM. It's then possible to use either buffered mode or direct mode (which uses CTRL-W to toggle read-only/read-write).

Okay I'm trying my hand at the BS utility. It compiles just fine. But when I go to use it, this is all I can get. Right now I have 7,668 bytes stored via the regular interface, so I would assume I'd see something more meaningful than this.

Context:

• Linux: 6.5.0-35-generic #35~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Tue May 7 09:00:52 UTC 2 x86_64 x86_64 x86_64 GNU/Linux,
• Screen version 4.09.00 (GNU) 30-Jan-22

I'm afraid it's not working properly in this context with "screen": after intial connect it scrambles content and freezes. Reconnect doesn't help. Ctrl-W does not toggle back and Ctrl-L, Ctrl-G, are not working.
Are you sure that this configuration is supported?
I switched to minicom as it appears much more stable.

This isn't really a feature request. It's more of a tutorial / possible inspiration for whoever comes across it. Wasn't sure where else to put it.

As an experiment to see how much data I could cram onto my Blaustahl, along with encryption... I put everything I wanted into a text file, saved it as "pw.txt", then ran...

brotli pw.txt
openssl enc -aes-256-cbc -salt -in pw.txt -out pw.txt.aes
base64 -b 80 -i pw.txt.aes -o pw.txt.aes.b64

The result was compressed, encrypted, and Base64 encoded... resulting in 2,564 bytes stored in 1,587 bytes.

Then I opened the .b64 file up with a text editor, opened the Blaustahl interface via Screen, switched on write mode, ensured the cursor was at the very beginning, then copied and pasted 24 rows at a time, pasting into the Blaustahl interface. It worked like a charm! (Note: the status bar may get in your way - if you can't hide it, you might try pasting 23 rows at a time instead and leaving the status bar line blank)

For the fun of it, I then copied it all back out a page at a time, ran the process in reverse, and there was all my data. :)

Now it would be cool if this was all built in somehow - but even if it isn't, doing it manually isn't too hard. I wouldn't want to do much more than 8KB, though haha

Hello! Loving my Blaustahl so far.

A few feature suggestions for the built-in text editor...

• CTRL+A: Go to the beginning of the line
• CTRL+E: Go to the end of the line
• CTRL+K: Delete entire line
• PGUP: Move cursor to top, then if pressed again (or already on bottom), go to the next page up
• PGDN: Move cursor to bottom, then if pressed again (or already on bottom), go to the next page down
• When pressing ⬅️ at the beginning of a line, it would be nice if it would go to the end of the prior line
• When pasting information, it would be nice if it would erase the entire line. If you have "abcdefg" and paste "123" with the cursor on "a" you'll end up with "123defg". It would be helpful if it would go ahead and nullify the rest of the line as well.

Bugs in the text editor

• I'm running v0.0.4 and when I press CTRL+S to hide the status bar, it doesn't appear to do anything?
• When on the last column #80 on any line, if you type a character, you can't backspace it out. Only the delete key will remove it - except a lot of keyboards don't have a delete key.
• Backspacing out the final line removes one character at the end of the previous line: https://v.usetapes.com/OwkU6QexWE

You need to also store the firmware in durable storage, else when the flash holding the firmware forgets it the device is bricked.

Windows fails to recognize the device when running the (default) USB composite firmware.

As a workaround there is now an alternative CDC-only firmware that is successfully recognized by Windows.