Librevault: Open source zero-knowledge peer-to-peer file sync | Hacker News Reader

Librevault: Open source zero-knowledge peer-to-peer file sync

librevault.com

99 pointsim_dario30 comments

I wish people would stop using the phrase "zero knowledge" willy nilly. It has a specific meaning within cryptography.

Yeah... I kept looking for the way this is ZK. Do they just mean that the files are encrypted on their servers and so they can't read them?

I understand accidentally stepping on a term from an adjacent field, but using it this way for a product that presumably is crypto-centric is a bit of a red flag.

I have no server infrastructure. ZK in this context means, that you can create an encrypted share. But, I think, it is not an appropriate term here.

Can you describe your file encryption procedure? In the Meta::Chunk class the 'encrypt' function only computes AES-CBC with no MAC, but there are calls to compute_strong_hash at other points in the library. There are references to a (non-cryptographic) Rabin hash as well as SHA2-224 and SHA3-224 in these functions - which is used for ciphertext authenticity and integrity?

During the indexing procedure, the value of SHA3-224(AES256(data)) is computed for each chunk.

Then, the list of these hashes is placed into Meta structure. After that, this Meta is ECDSA-signed using a EC point, decoded from A-type secret.

Any other type of secret contain the public part of EC point and can verify the signature.

So is there a per-chunk MAC, or do you rely on the signed hashes of ciphertext for the integrity and authenticity of each chunk?

Actually, there is per-chunk HMAC support in the protocol and present revisions add HMAC for each chunk into Meta: https://github.com/Librevault/librevault-common/blob/master/...

This HMAC is computed over plaintext chunks and used to determine, if we already have this chunk in database (because of random IV we get different hash of ciphertext every time), not for verification.

And what is wrong about verifying integrity and authenticity by hash-then-sign?

Maybe nothing, but it's just kind of a weird, nonstandard way of doing things. Also it's not immediately obvious to me that your method meets modern security definitions like IND-CCA2.

Please add some basic instructions on how to use this on a local network.

I tried the following:

1. Download app and install

2. "Add folder" new key, select folder I want to sync. Ok. Folder did not then appear in the list as expected. It should it appear in the window straight away, right?

3. I then installed the software on another computer.

4. On other computer clicked 'Open URL' and added "lvlt:<secret_key_from_step_2_above>". OK. This did nothing either.

Where am I going wrong. Please add a basic getting started to your site which shows the basic steps to add a folder on one computer and then set up another computer to sync the folder down onto.

Looks like a great little app. thx in advance for your assistance.

Sounds awesome. I think your website could use an explanation of the term "zero-knowledge".

Thank you for advice. This revision of the website is a stub, it does not contain any useful information, just some general words. It will be heavily reworked soon.

Also, I will add the comparison table with Syncthing, BTSync and some cloud storages, like Dropbox.

Have you thought about just not using the phrase "zero knowledge" at all?

I don't use it on GitHub page. It updates more frequently than the site. The next revision of the website will contain a new motto, but I have to make a new motto first.

Very nice. It seems a lot less janky than Syncthing (web UI, constant process restarts)

SyncTrayzor (windows client implementing synching) is pretty nice. It runs as a tray icon but when you click it, it loads like a native app even though it's a web app (similar to electron)

But it is still a web ui, not a native one. Also, SyncTrayzor itself is not cross-platform, so Linux users have to install syncthing-inotify for watching the directories for changes.

It's network compatible with and syncthing clients. Syncthing is an open standard with dozens of client apps.

My thoughts exactly. I might give this a spin. Here's hoping it has "Folder Master" support.

Looks great! Any plans to document the synchronization protocol?

I've been using SyncThing but it lacks the main feature I need, which is to selectively synchronize only certain files to other devices.

Yes. The protocol is pretty stable now, it hasn't been changed for a while and has necessary extension points, so I can add more features in the future. I will publish the protocol specification in two weeks.

Are there any plans for a headless server. I'm still looking for a good way to sync my NAS to my desktop.

It is headless by design. GUI and synchronization daemon are separate applications, that communicate using the WebSocket protocol. So, you can install your sync daemon to NAS and you are good.

But to let you control the daemon via the net, I am making Web UI, that will enable you to fully control synchronization process from your browser.

Something I just noticed after testing Librevault today... Extremely low CPU/power consumption. Nice!!!

How does it compare to syncthing et al?

There are certain differences between Librevault and Syncthing now:

* Librevault is simpler for the end user. From my perspective, Syncthing doesn't aim to be user-friendly. More like geek-only solution.

* Librevault supports adding a folder by key, like BTSync. And also, it supports a URL scheme for adding a new folder just by clicking it in the browser: https://librevault.com/blog/lvlt-scheme/

* inotify, fsevents, kqueue and ReadDirectoryChangesW support out of the box. Syncthing requires you to install a separate third-party plugin for this.

* DHT support, so it doesn't need any trackers for peer discovery. DHT is Mainline DHT, so it can connect to BitTorrent clients and ask them for peers. It means, that Librevault can participate in the world's largest distributed peer discovery network and will not suffer the lack of DHT nodes.

Also, it has a proper (!) desktop UI inspired by BitTorrent Sync 1.3.

Geez, that's what I am exactly working on off-work, slowly but the idea is nearly 100% identical.

Heh, me as well (https://github.com/rakoo/rakoshare) although I've been trying other technologies and combinations lately, slowing the development a lot.

Maybe, you have a GitHub page?

Looks interesting I am looking for a new private file sync application. Any plans for Arch Linux (Can build it myself but find AUR easier) and android?

Yes, I am planning versions for Arch and Fedora soon. Android version is in plans, too, but I need to make desktop version stable first.

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