Any way to decrypt files encrypted by secrecy in windows/linux?

[alete89]

Pretty much self-explanatory. Is there a way?
Thanks.

[nicogarcia]

+1 👍

[langston-barrett]

I've tried to copy the files onto my PC and run

openssl aes-256-cbc -d -in c2lnbmFsLTIwMTctMDEtMDgtMTcxNDIy.jpg -out plain-text.jpg

but haven't had any luck yet. Not sure whether or not CBC/CTR/ECB is the default (or if that sentence even makes sense). It seems that the files are also encrypted using a vault-specific salt, so it might be hard to decrypt without knowing it.

I think we'll need some kind of officially supported export.

[minusdavid]

I'm very much interested in this goal as well.

After browsing the code, it looks like the salt and other encryption details are stored in the .vault file. I imagine the password hash is also stored there but I haven't had time to verify yet. But at a glance it seems like the details in .vault should be

[minusdavid]

Enough to get a person the key for decryption.

I've only looked at the source for a few minutes today so not sure if each file has its own encryption key (like Facebook's f4 object storage) or if all files use the same encryption key. I think it might be the latter but just haven't had the time.

I'm hoping to find some time to try to make a little Java utility that can unlock a Secrecy vault, and then probably port that to Python and Perl for convenience if possible.

Of course, I have a million pet projects I'd like to spend time on, but this one would be fun.

[minusdavid]

I'd love to add some unit tests to this codebase too. That would make this type of task way easier
...

[minusdavid]

At a glance, it seems like .vault might be encrypted, but according to the source it looks like it's actually just a serialized data structure using Google Protocol Buffers.

So sometime soon I'll look at examining the .vault header on a desktop and see if I can decrypt files in a vault from there...

[minusdavid]

https://developers.google.com/protocol-buffers/docs/reference/other

[minusdavid]

Btw, it looks like the salt is in the .vault header so that should get us that bit closer.

Notwithstanding the bug with not being able to access the external sd card, interoperability with other operating systems is my only other wishlist item really...

[minusdavid]

Here's the protocol buffer definition to use with the protocol buffer compiler for the desired lang:

https://github.com/SecrecySupportTeam/secrecy/blob/master/app/src/main/java/SecrecyHeaders.proto

[minusdavid]

Using the Python tutorial for Protocol Buffers (https://developers.google.com/protocol-buffers/docs/pythontutorial), I've been able to access the salt, the vault initialisation vector, the pbkdf2iterations, and encrypted aes key, which are all stored in .vault. I'm working on Ubuntu on Windows (on Windows 10). So that's cool.

It looks like each file header also contains an initialisation vector for the file and the filename which will be needed for decrypting the files I reckon.

Now to convert the decryption logic from Java to Python...

[minusdavid]

Starting to think it might not be worth doing this in Python (at least to start) and that it would be smarter just to use Java to start off with...

[minusdavid]

I'm glad that I switched to Java from Python. Trying to find equivalent crypto functions in Python was a nightmare. Most of the Java classes are part of the standard library, so it's easy enough to replicate the functionality from the Android app. The only difference is that you need to install BouncyCastle on your system, since it's already baked into Android. But it's available in the Ubuntu 14.04 repositories.

[minusdavid]

I have written a little Java tool which can decrypt files from an encrypted Secrecy backup. I have verified it by adding a file to Secrecy on an Android phone, taking a backup on the Android phone (ie zipping the files), and then copying that backup over to a desktop. On the desktop, I run the Java tool using some command line arguments, and it successfully decrypts the chosen file and saves it to a clear file on disk.

It's an extremely rough draft at the moment, but I'll look at polishing it up and sharing it on Github. (So I'll host a repo and share the link here.)

@alete89 : I reckon it'll do what you need.
@siddharthist : Since it'll do the decryption, you can probably close your bug about an openssl compatible format. Although I had actually thought about going that route at one point when I found Python didn't have the key unwrapping functionality I wanted. In the long-run, it would be interesting to see if a person could do it in Python or with openssl, but... the Java tool works.

I'll try to include explanatory notes in the code. It looks like the .vault file is encrypted with aes-gcm and the individual files with aes-ctr. Well, newer versions of Secrecy would be with aes-ctr I think. I don't know about older ones. Older ones might be aes-cbc or aes-ecb. I think those have just been retained for backward compatibility.

Anyway, the tool seems to work well enough for retrieving data from a backup. I will probably extend it to do things like list files as well so you know what you want (I just happened to know the encrypted filename of what I wanted).

It would be nice to have a GUI for this though. I've only played with WPF and Qt, but I think Java has a number of GUI options. Who knows... maybe I can try to reverse engineer the Java a bit to see if I can get this working with C++ or C#. (Python wouldn't be much help for a GUI project so probably no point going that route in any case.)

[Graveen]

Very interesting. Kudos !