Shared posts

10 Aug 21:00

USENIX Security Best Paper 2016 – The Million Key Question … Origins of RSA Public Keys

by Dan Cvrcek

Petr Svenda et al from Masaryk University in Brno won the Best Paper Award at this year’s USENIX Security Symposium with their paper classifying public RSA keys according to their source.

I really like the simplicity of the original assumption. The starting point of the research was that different crypto/RSA libraries use slightly different elimination methods and “cut-off” thresholds to find suitable prime numbers. They thought these differences should be sufficient to detect a particular cryptographic implementation and all that was needed were public keys. Petr et al confirmed this assumption. The best paper award is a well-deserved recognition as I’ve worked with and followed Petr’s activities closely.

The authors created a method for efficient identification of the source (software library or hardware device) of RSA public keys. It resulted in a classification of keys into more than dozen categories. This classification can be used as a fingerprint that decreases the anonymity of users of Tor and other privacy enhancing mailers or operators.

Bit Length of Largest Prime Factors of p-1
The graphs extracted from: The Million Key Question – Investigating The Origins of RSA Public Keys (follow the link for more).

All that is a result of an analysis of over 60 million freshly generated keys from 22 open- and closed-source libraries and from 16 different smart-cards. While the findings are fairly theoretical, they are demonstrated with a series of easy to understand graphs (see above).

I can’t see an easy way to exploit the results for immediate cyber attacks. However, we started looking into practical applications. There are interesting opportunities for enterprise compliance audits, as the classification only requires access to datasets of public keys – often created as a by-product of internal network vulnerability scanning.

An extended version of the paper is available from http://crcs.cz/rsa.

30 Dec 21:00

32C3: Inside Glorious Leader’s Operating System

by Brian Benchoff

North Korea is a surveillance state propped up by a totalitarian government infamous for human rights abuses and a huge military that serves the elite while the poor are left to fight over scraps. Coincidently, that’s exactly what North Korea says about the United States.

There is one significant difference between the two countries: North Korea has developed its own operating system for its citizens, called Red Star OS. It’s an operating system based on Linux, but that has a few interesting features that allow Glorious Leader to take care of his citizens. A deep teardown of what has gone into the development of Red Star OS hasn’t been available until now, with [Florian Grunow] and [Niklaus Schiess]’s talk at the Chaos Computer Congress this week.

Kim Jong-Un with an iMac
Kim Jong-Un with an iMac

The first question anyone must ask when confronted with an operating system built by a country that doesn’t have much electricity is, “why?” This question can only be answered philosophically; the late Kim Jong-Il stressed the importance of North Korea developing “their own style” of programming, and not relying on western operating systems. Nearly everything in Red Star has been modified, with a custom browser called Naenara, a crypto tool, a clone of Open Office, a software manager, and a custom music composition tool. Red Star also had to have the look and feel of OS X; that is, after all, what Glorious Leader uses.

Red Star goes much deeper than custom browsers and a desktop theme. There are other, subtler components inside the OS. There is a program that verifies the integrity of the system by checking signatures of the custom files against a database. If a file has been tampered with, the system reboots. Since this tamper check runs on bootup, Red Star makes it nearly impossible to modify files for study. This is one of the big features designed into Red Star – system integrity is paramount.

There are other custom bits of software that hide files from the user even if they have root, and a ‘virus scanner’ that is anything but. This virus scanner checks documents for patterns that, when put through Google Translate, are strange, weird, and somewhat understandable. Phrases like, “punishment”, “hungry”, and “strike with fists” are detected in all documents, and depending on what the developers decide, these documents can be deleted on a whim.

While scanning a system for documents that contain non-approved speech is abhorrent enough, there’s another feature that would make any privacy advocate weep. Media files including DOCX, JPG, PNG, and AVI files are watermarked by every computer that opened the files. This allows anyone to track the origin of a file, with the obvious consequences to free speech that entails.

While most people in the US consider North Korea to be a technological backwater and oppressive regime, the features that make Red Star OS useful to the DPRK are impressive. The developers touched nearly everything in Red Star, and the features inside it are rather clever and make their style of surveillance very useful. They’re also doing this without any apparent backdoors or other spycraft; they’re putting all their surveillance out in the open for all to see, which is, perhaps, the best way to go about it.


Filed under: cons, linux hacks