Category Archives: Security

Decrypting your Frozen Mobile Phone

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The idea is not new, but the implementation is new, interesting and eye-catching. Tilo Müller and Michael Spreitzenbarth of FAU managed to implement FROST: “Forensic Recovery of Scrambled Telephones”.

The story in brief goes like this: Android phones from version 4.0, have a built-in option to encrypt all data on the storage device. Obviously data is decrypted on the fly when needed and stored not encrypted in the memory (RAM). When not needed anymore or the phone is turned-off, all un-encrypted data in RAM is very carefully deleted.

So what you do is to remove the battery with the phone on and then immediately restart the phone performing a so-called “cold.-boot”. In principle by removing the power all data is lost in the RAM and maintained (encrypted) only on the storage device. But it takes some (short) time for the RAM to forget all data, and this time depends on the kind/material of RAM chip and its temperature. Müller and Spreitzenbarth discovered that if the temperature of the chip in some Galaxy Nexus devices is below 10 degrees Celsius (please put your phone in the fridge…) then you have just enough time to read the unencrypted data in the RAM after the cold-boot, without need to know the password or PIN.

Enjoy the pictures on their website!

More on Java, Updates and Security

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Oracle has announced (see here for the official page) that on February 19th a new Java Critical Patch Update will be released which will fix the February 1st patch. But what worries me most is that the next updates are scheduled for

  • 18 June 2013
  • 15 October 2013
  • 14 January 2014.

In my opinion this indicates that Oracle has not yet managed to implement the software development and patching cycle in the correct way, or otherwise it should have been possible to release scheduled monthly updates. We know that it is not easy to do, but Oracle’s competitors have been able to, so what is going wrong with Oracle’s software development practices?

What’s happening with Java ?

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The Java situation for what concerns the security in particular of the Java Runtime Environment and of web plugins, is not clear at all.

Oracle gives very little information about what is going on, but at the same time it makes public a meeting among its top  JRE responsible out of which it is not clear what to conclude. Some commented saying that this public relation move has backfired.

Some technical experts claim that it will take at least 2 years to clean up the Java code, not considering the new vulnerabilities which will be discovered.

Apple releases an update to Xprotect which bans Java plugins up to a version which was not yet released by Oracle at that moment. This in practice prevented the users to use Java plugins until Oracle released the new version. (BTW, it is not difficult to modify the XML configuration file of Xprotect to relax this condition, if you can access the OS as root.) Not clear information has been given also in this case neither by Apple nor by Oracle.

So we as users seem to be wandering in the dark and hoping for the best.

UPDATE: Oracle released a new Java version in a hurry, see eg. here for more info.

Cryptography as Liability Shift

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Everybody seems to be talking about Kim Dotcom’s new Mega file-sharing service. What arouse my interest is the use of cryptography. I did not look into it in details but from what I read (for example here) it should work as follows:

  • access to the service is only through a browser and the code executed in the browser is written in JavaScript;
  • at the moment of creating an account, the users chooses a password which is not sent to the server, instead from the password the browser derives an authentication token which is shared with the server; the server cannot recover the password from the authentication token;
  • the browser generates an encryption key with which all data sent and received by the server is encrypted and decrypted by the browser itself: the server hosts only encrypted data and has no access to it since it does not know the encryption key;
  • for user convenience, the encryption key is stored also on the server but encrypted with the password, in this way the server has no access to the encryption key but the user can retrieve it when he needs it.

This general idea of this approach is of course not new, but the way in which it is implemented leaves a lot to think about. Everything is delegated to the browser and implemented in JavaScript, this means for example that it is not so hard to add (or modify) a JavaScript to obtain the password and send it to any other server. This is indeed what most online banking malware do by injecting in the browsers a few lines of JavaScript in the home pages of the online banking websites’ pages. This is also what at any moment the Mega service could do, without the user ever know it. On top of this, many other points should be checked like for example if the implementation is sound from a security point of view, and we very well know that it is not at all easy to implement cryptographic protocols the first time without making any mistake.

So what is the point of all of this? Well, the first thing that comes to my mind (and to other bloggers’ mind) is that the primary purpose of all of this is not to protect the users and the users’ data, but to allow Kim Dotcom to discharge any legal responsibility on the contents hosted on his servers. Since users’ data is encrypted by the browser on the users’ PC and the server has no access in clear to the encryption keys, then all the responsibility on the data hosted on his servers is of the users.

I am curious to see how this will develop.

UPDATE: there are already search engines to find illegal material to download from Mega…

Computer Security from bottom-up with a “clean slate”

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This is my first post in my new blog and I would like to start with this interview to Robert Watson (Cambridge University UK) on IEEE Spectrum which I found interesting. The main points in my opinion are:

The role of operating system security has shifted from protecting multiple users from each other toward protecting a single…user from untrustworthy applications.…Embedded devices, mobile phones, and tablets are a point of confluence: The interests of many different parties…must be mediated with the help of operating systems that were designed for another place and time.

[…]

in historic systems, large multiuser computer systems, you know, we had these central servers or central mainframes, lots of end users on individual terminals. The role of the OS was to help separate these users from each other, to prevent accidents, perhaps to control the flow of information. You didn’t want trade secrets leaking from, perhaps, one account on a system to another one.

[…]

So the observation we make on these new end-user systems like phones is that what we’re trying to control is very different. The phone is a place where lots of different applications meet. […]  And on phones today, we encourage users to download things all the time. So what has changed now? Well, we’ve deployed something called sandboxing inside of these phones so that every application you download runs inside its own sandbox. And that is a very different use of security. And it is provided by the operating system, so it’s still a function of the operating system.

The main point is that we should re-think security from bottom-up starting with a new paradigm for the OS primitives, the main scenario which we should add to the historical one is the single-user multiple-untrusted applications, whereas all our OSes have been designed for the multiple-users multiple-trusted applications scenario.

This also reminds me of Qubes and Bromium which are efforts to obtain a larger control on applications by using microkernels and Virtual Machines as underlying OS.

An article by Watson will be published in the February 2013 issue of Communications of the ACM.