Many many moons ago, I started Syncany, a small open source file synchronization project that allows users to backup and share certain folders of their workstations using any kind of storage, e.g. FTP, Amazon S3 or Google Storage.

At the time of the initial annoucement of the project (May 2011), there was a big hype around it. I received many e-mails and lots of support from people around the world. People were excited because the features Syncany offers are great: File synchronization à la Dropbox, paired with storage flexibility (use-your-own), client-side encryption (sorry about that, NSA!), and intelligent versioning.

At the time, I didn’t actually release a runnable version of Syncany. The sole purpose of the announcement (on WebUpd8 and on the Ubuntu Podcast) was to get developers excited about the project in order to get help for the last steps of creating a somewhat stable release. Unfortunately, I was further away from this “stable release” than I could have imagined.

In this blog post, I’d like to recap the idea behind Syncany, what went wrong with the development, and how I brought the project back on track (or so I believe). I’ll also talk about what I plan to do with Syncany and how people can help (if they still want).

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I recently demonstrated how to perform a man-in-the-middle attack on HTTP(S) connections using mitmproxy. While mitmproxy works just great for HTTP-based communication, it does not understand other TLS/SSL-based traffic such as FTPS, SMTP over SSL, IMAP over SSL or any other protocol wrapped in TLS/SSL.

SSLsplit is a generic transparent TLS/SSL proxy for performing man-in-the-middle attacks on all kinds of secure communication protocols. Using SSLsplit, one can intercept and save SSL-based traffic and thereby listen in on any secure connection.

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The Domain Name System (DNS) is one of the fundamental services of the Internet. By resolving domain names to IP addresses, it makes routing of IP packets possible and thereby lets browsers and other clients connect to remote servers using all kinds of protocols. By blindly connecting to the IP address returned by the DNS server, however, users put a lot of trust into DNS, because by default, DNS responses are not validated or verified.

In this blog post, I’d like to demonstrate how to easily set up a DNS server that allows you to easily forge certain entries manually — thereby allowing you to either block certain domains from your network or to pretend that you are a certain website. This scenario is commonly referred to as DNS forgery or DNS spoofing.

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I use rsnapshot to backup all of my data to my HTPC and home server (the home partition, office documents and the root file system). While rsnapshot is not as shiny as other backup tools, it is very flexible and effective: rsnapshot is based on rsync and makes hardlink-based backups (like cp -al), i.e. backups that point to the same inode on the disk if a file in consecutive backups is identical (much like SIS in deduplication).

However, rsnapshot is meant to be triggered by cronjobs and is built for always-on server machines rather than for lid-open-lid-close-type machines like laptops: That means that rsnapshot must be scheduled to run at a certain time (no retries!) and is not prone sudden system shutdowns. Furthermore, it does not detect failures and simply leaves unfinished backups as if they were complete. That in turn leads to more disk space being used for the backups, because the last complete backup is not really complete.

I wrote a little helper script to fix exactly this behavior: rsnapshot-once makes sure that (1) rsnapshot is only called if a backup is necessary (once every 24h for ‘daily’, once ever 7 days for ‘weekly’, …) even if rsnapshot-once is called multiple times, and (2) that crashed/interrupted backup runs are rolled-back before starting a new backup run.

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This post introduces my Master’s thesis “Minimizing remote storage usage and synchronization time using deduplication and multichunking: Syncany as an example”. I submitted the thesis in January 2012, and now found a little time to post it here.

The key goal of this thesis was to determine the suitability of deduplication for end-user applications — particularly for my synchronization application Syncany. As part of this work, the thesis introduces Syncany, a file synchronizer designed with security and provider independence as a core part of its architecture.

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In some situations it is necessary to hide binary data in another file format so that it cannot be easily detected — be it to store data on image storage platforms such as Picasa, or to circumvent firewalls or mail filters. I wrote a little helper to encode byte arrays, streams or files into 24-bit bitmap images (BMP files).

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