Dexios
What is it?
Dexios is a command-line file encryption utility, suitable for encrypting files before uploading them to a cloud-service. It is written entirely in rust and contains no unsafe code (some dependencies may contain unsafe code, but they have received the correct audits and are deemed secure).
It uses AES-256-GCM encryption with argon2id to generate the encryption key.
It has been tested on Void Linux, but more platforms will be tested in the future.
For securely erasing the file, it's about as good as we will get. It doesn't factor in how the host OS handles things, or the filesystems. It overwrites the file with many random bytes, and then with zeros, before truncating it and "removing" it with the OS.
Building notes
As mentioned in the AES-GCM crate docs, please enable certain flags while building. For example:
RUSTFLAGS="-Ctarget-cpu=native -Ctarget-feature=+aes,+sse2,+sse4.1,+ssse3"
Change native to whichever CPU family/model you are going to be running the code on, if it's going to be ran on a different machine.
Checksums
Hashing mode uses Blake3 for verification, due to it's speed, security and regular updates. (very ideal for this use case).
This was originally sha3-512 in versions 3.x.x and below, and was KangarooTwelve in 4.x.x (via the tiny_keccak crate) but since v5 it has been changed to Blake3 for a number of reasons.
The tiny_keccak crate hasn't received updates in a long while, and is no longer actively maintained.
The k12 crate is ideal for this situation - but it is rather immature compared to some other hashing implementations, so Blake3 will be our main hashing algorithm, and there are no plans to change this as of yet.
Blake3 also offered some marginal performance benefits, but this could be due to a number of factors.
Performance
Tests were ran on a system with a Ryzen 7 3700x and 16gb of 3000MHz RAM - running Void Linux. The file used was originally 3.5GiB, and it was stored on a Cruicial MX500 SSD.
Version 6 removed JSON entirely, and dropped base64, which really shows in the performance metrics.
The time was determined via /usr/bin/time -f "%e"
| Version | -esyk | -dsyk |
|---|---|---|
| 3.2.8 | 44.37s | 40.91s |
| 4.0.0 | 23.70s | 30.43s |
| 5.0.0 | 22.48s | 28.66s |
| 5.0.2 | 20.14s | 21.26s |
| 5.0.9 | 19.31s | 18.92s |
| 6.0.0 | 11.74s | 11.59s |
Output file sizes
In versions 5.x.x and below, the 3.5GiB test file was encrypted at 4.72GiB - this involved a lot of overhead for base64 and a tiny amount with the JSON.
As of version 6, JSON and base64 has been dropped entirely. This has reduced the file size down to be marginally higher than our 3.5GiB test file (284 bytes higher, to be exact).
Environment Variables
Dexios can read your key from an environment variable! Just set DEXIOS_KEY and it will automatically be detected and used. Due to using different salts and nonces for every encryption, there is no inherent risk in reusing keys - although it's not a good security practice.
Key Inputs
The priority is as follows:
- First, Dexios will check for whether or not you have specified a keyfile (via
-kor--keyfile) - If no keyfile is detected, it will look for the
DEXIOS_KEYenvironment variable - If neither of the above are found, you will be shown a prompt to enter a password manually
Usage Examples
To encrypt a file, and show the hash of the encrypted (output) file for verification later on:
dexios -es test.txt test.enc
To decrypt a file, and show the hash of the encrypted file beforehand (to compare with the hash generated above):
dexios -ds test.enc test.txt
To encrypt a file, and erase the original file:
dexios -e --erase test.txt test.enc
To use a keyfile for encryption:
dexios -ek keyfile test.txt test.enc
To encrypt all .mp4 files in a directory, we can use find. This works a LOT better with a keyfile/environment variable key as you will have to input the password manually each time otherwise. It will append .enc to the end of your files. You can remove -maxdepth 1 to make this run recursively.
find *.mp4 -type f -maxdepth 1 -exec dexios -esyk keyfile {} {}.enc \;
To encrypt all .mp4 files in a directory, and remove the original files once encrypted:
find *.mp4 -type f -maxdepth 1 -exec dexios -esy --erase -k keyfile {} {}.enc \;
To Do
- Error handling
- Ensure the encryption and decryption functions are air-tight
- Add a secure-erase function for the input/source file
- Run some more tests, specifically on large files
- Test keyfile functionality
- Don't show stdin text when entering password inside of the terminal
- Add checks for output files so we don't overwrite any by mistake
- Hash the file before encryption and after decryption, so the user can confirm the data is exactly the same
- Use clap subcommands instead of arguments to make it easier to use
- Optimise reading the input/output files, so less disk usage
- Find a way to encrypt large files (larger than the system's memory) - this is just another optimisation though
- Optimise memory usage in general too
- Further optimise the reading and handling of the data, especially in memory.
- Larger files in
hashingmode will causedexiosto force quit, due to absurdly high memory usage. This is because the data is being copied in memory multiple times, instead of re-using the same buffer. I believe this needs aCursorto resolve, and a patch will be released once I have found the best solution.
- Larger files in
- Refactor/split everything into semi-specialised files, to make the codebase more maintainable
- Add benchmarking switch that doesn't write to the disk
- Manually
zeroizesensitive data in RAM
![[FEATURE] Encrypting a Directory](https://avatars.githubusercontent.com/u/77554505?v=4)
![[BUG] --auto parameter](https://avatars.githubusercontent.com/u/107638197?v=4)
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