Thursday, December 17, 2009

Recent Uploads to Scribd, Dec 17

Here are my recent document uploads to Scribd

Sunday, December 13, 2009

A USB Entropy Drive

A UK company called Simtec Electronics has created a USB thumb drive device with dedicated hardware for producing a continuous stream of high entropy bits, suitable for mixing into an existing entropy pool on your device or feeding directly into applications and protocols that require sources of randomness. The product is called Entropy Key and and can be ordered from the website for £36.00, with further discounts for bulk orders

An overview of the process for producing the entropy is given in the diagram below. There are two independent noise generators based on P-N junctions that are sampled at a high rate to produce a stream of bytes. The output of each generator and their XOR are subjected to the universal statistical bit test devised by Ueli Maurer. If the sequences pass this test then von Neumann’s debias trick is applied, and then another round of universal testing, followed by hashing with Skein. This process blocks at any stage if the computed statistics fall outside conservative estimates of the properties of random generators.


These steps are repeated until 20,000 bit have been collected, upon which the statistical tests recommended by FIPS 140-2 are applied. The 20,000 bit pool is then parcelled into blocks of 256 bits, and Simtec estimates that each such bock has been generated from about 5,000 bits of noisy hardware samples.

There is quite a reliance on Maurer’s universal statistical bit test, and perhaps justifiably so since this test is specifically designed to detect deviations from expected statistical properties in a bit generator by computing an estimate of the generator’s entropy using ideas from universal data compression algorithms. The test is quite simple, and there is a reasonable description and parameterization given in NIST SP-800 22, which also contains a description of a large number of other statistical tests. A research paper on a finer analysis of Maurer’s test can be found here.

The output rate is, by its nature, variable but an average rate of more than 30 kilobits per second is expected. The complete client daemon source is provided under an MIT license which means everyone is free to examine the code for themselves. SimTec also notes that the Entropy Key can automatically detect various different physical attacks, such as temperature changes (by using a built-in temperature sensor), and opening of the case. The device is currently undergoing testing with "select customers” but is available for general ordering. There is an IRC channel #ekey on the oftc network if you want to discuss any of this further.

(Thanks to Vincent Sanders for providing some more technical details)


Saturday, December 12, 2009

A Faraday Wallet

Do you remember the blocker tag? This was a proposal from researchers Ariel Jules, Ron Rivest, and Michael Szydlo, all affiliated with RSA Data Security, published (and surely patented) in 2003. It was about this time that the privacy concerns over information that could be collected about you and your habits by engaging in passive exchanges with arbitrary RFID readers was reaching its zenith. Your RFID tagged items could be passively giving away a lot information without your consent or knowledge.


Jules, Rivest, and Szydlo jokingly suggested that you could encase yourself in protective foil or mesh, which would make walking a bit more awkward but perhaps could be useful for wallets. And now we have just such a wallet, shown below.


It is advertised as an Identity Theft Preventing Privacy Wallet, retailing for $79.95. The product advertising states that

Most credit cards now contain tiny chips that provide a unique identifier that can be scanned to retrieve your billing details.

Such RFID technology can, unfortunately, also be corrupted by hackers using portable scanners in crowded airports, restaurants, and stadiums. Our slim and surprisingly lightweight Privacy Wallets are literally woven from over 20,000 super-fine strands of stainless steel into a flexible fabric that feels like silk — but protects your ID like armor plate! Stronger than leather, with no sharp edges or corners — and won’t stain or scratch.

Inside, 6 credit card slots, 2 internal slots, and a billfold let you carry plenty of purchasing power — completely shielded from today’s high-tech pickpockets.

This could go well with your swine flu suit.

Thursday, December 10, 2009

The Crypto Year in Review from Bart Preneel

Bart Preneel is a professor at the Katholieke Universiteit Leuven, in Brussels, and leader of COSIC, one of the largest security and cryptography research groups in Europe. This is the research group that produced Rijndael, which eventually became the AES. Preneel is a frequent speaker on security and cryptography, and in this post we will review a recent presentation on the topic of the Crypto Year in Review.

Preneel begins by observing that cryptographic research is alive and well, with over 600 papers published on the pre-print server of the IACR, amounting to over 10,000 pages of written research. Not all of these papers will be published, but it does give you some idea of the reading load to keep abreast of new ideas and developments.

His attention then turns to AES, which still remains secure despite the publication of several theoretical attacks. AES now runs at 110 MB/seconds in software, and Intel has announced direct hardware support beginning with its Westmere line of chips. Referring to the security of AES-256, Preneel states that for $5 billion USD, a key cracking device could be built to search a 120-bit key space that would take a billion years. This was about the same work required by the so-called Luxembourg Attack announced in June, which was the first attack against full AES-256 that saved significant time over exhaustive search (though a large amount of ciphertext is required).

Preneel calls this an academic weakness, since it relies on a related key attack which is hard to arrange in practice and can be easily avoided by making the AES key schedule more non-linear. The slide below shows that relationship between AES key size and the number of rounds. There are several feasible attacks when the number of rounds is 10 or less with small key sizes. The 2^{119} effort of the Luxembourg Attack is located far above what is considered practical.


Preneel then considers hash functions, the topic of his PhD thesis. He gives a benchmark slide showing the complexity of collision attacks against well-known hash functions, assuming a $100K USD funded adversary using special hardware (equivalent to 4 million PCs).


The downward trend of the graphs is suggestive of a meltdown for hash functions, with the worst implications for protocols and signatures yet to play out. The transition path to a better hashing standard via the SHA-3 hash contest of NIST in underway, and a new standard by will be selected by 2012. However Preneel is concerned that the design of SHA-3 will be based on state-of-the-art from 2008 – that is, all of the additional insights and learnings produced in the evaluation of the SHA-3 candidates will not be exploited until SHA-4.

It was a relatively quite year for public key cryptography, with no factoring records announced, but a lot of fretting over the coming upgrade of RSA-1024 keys in 2010 in compliance with US standards. Elliptic curves are rising in importance due to support from the NSA, and quantum computers remain a very long term threat to the security of public key systems.

There are some additional topics considered by Preneel, mainly around protocols and deploying cryptography. His summary is that 2009 was a relatively unexciting year on the surface but you may find interesting details when you look closer. Also, always remember that cryptography is a building block for information security, an essential block but far from the whole story.

Monday, December 7, 2009

WPA Password Cracking in the Cloud for $34


Following on from the recent results of a project on the feasibility of password cracking using cloud computing, a new cloud service for cracking WPA passwords has been announced by researcher Moxie Marlinspike, best known for his work on discovering subtle flaws in the SSL protocol. The cloud service attempts to crack uploaded passwords against a 135 million word WPA-optimized dictionary on a 400 CPU cluster.

The stated purpose of the service is to assist penetration testers and network auditors who need to test the strength of WPA passwords that use pre-shared keys (PSK or personal mode). In this mode, the PSK master key is used to derive a session key from several parameters in the initial wireless connection handshake, including the MAC addresses of the client and base station. In practice, the PSK is a password and is therefore exposed to a brute force or dictionary attack.

Verifying a guess for the PSK password is relatively costly, roughly the equivalent of processing a megabyte of data, since the session key is derived from 4096 iterated hash operations. This high iteration count, or spin, limits the number of password trials to several hundred per second on a standard desktop. Marlinspike's cloud service searches through a 135 million word dictionary in just 20 minutes, a computation that would otherwise take 5 days or so on a standard desktop.

And all this for just $34, after a client has uploaded a capture of the WPA handshake on the network of interest. If the cloud service does not find a password then a client can be confident that the submitted password is resistant to dictionary attacks – no refund, you still pay for the assurance!

The Church Of Wifi has a project to create public rainbow tables for WPA based on common passwords, but the resulting tables only encode one million passwords because the tables must be recomputed for each network identifier (ESSN), which acts as salt in the password derivation function. Marlinspike opted to create his own WPA-optimized dictionary list which includes word combinations, phrases, numbers, symbols, and “elite speak”.

In Security Muggles I posted about finding ways to connect with management about security. Robert Graham, CEO of penetration testing company Errata Security, has commented that "When I show this to management and say it would cost $34 to crack your WPA password, it's something they can understand," he said. "That helps me a lot."

PC World has somewhat dramatically reported the announcement as New Cloud-based Service Steals Wi-Fi Passwords, suggesting that the cloud is reaching into wireless networks and grabbing passwords. In fact, the service is designed to trade-off a 5-day desktop computation against a 20-minute cloud computation for $34. Nonetheless, a better name would be WPA Auditor rather than WPA Cracker.

Sunday, December 6, 2009

A Threat Model for SSL

I traced a link to my post How fast are Debian-flawed certificates being re-issued? to SSL Shopper, a new site for me, and I looked back through their news items and found a link to an SSL Threat model proposed by Ivan Ristić, the principle author of ModSecurity and a leader in Apache security.

Referring to the origins of his threat model, Ivan states that

SSL is easy to use but also very easy to use incorrectly. The ecosystem, which is built of the specifications, the implementations, the CAs and the PKI, is full of traps, each of which is very easy to fall into. Once I started to spend significant time thinking about SSL I set out to build a model of the ecosystem, for my own education and to ensure that I understand it all. That's how I arrived to the SSL Threat Model.

His threat model is represented as a FreeMind map, available as a graphic as shown below. The threat model considers clients, servers, PKI, protocols, users and attacks, and perhaps the model needs to be updated in light of the new The TLS Renegotiation Attack.


Ivan admits that the model needs some additional clarification, but it is probably more useful as a published draft rather than waiting for him to find the time to perfect the model (the same reasoning lead me to releasing my outline of a password book).

Tidbits: A5/1, WhiteListing and Google

There is a nice write-up in the very respectable IEEE Spectrum on the A5/1 rainbow table generation project run by Karsten Knol for cracking GSM encryption. The write-up for Knol in the IEEE is a signal that his project has mainstream acceptance and attention. The timeliness of Knol’s project was heightened a few weeks ago when MasterCard announced that they would be using GSM as an additional authentication factor in their transactions. This MasterCard feature may end up being very popular since IDC recently predicted that the mobile phone market will exceed one billion handsets by the end of 2010. Hopefully this huge demand will increase the deployment of the the stronger A5/3 algorithm that is being phased in during upgrades to 3G networks.

The evidence continues to mount that whitelisting is an idea whose time has come. Roger Grimes at InfoWorld published a large list of reviews on whitelisting products, and he was pleasantly surprised that “whitelisting solutions are proving to be mature, capable, and manageable enough to provide significant protection while still giving trustworthy users room to breathe”. Given that the amount of malware introduced in 2008 exceeded all known malware from previous years, viable alternatives to the current blacklisting model are needed.

Finally, Google recently announced that it will be offering its own DNS service, nominally to increase performance and security. Sean Michael Kerner wonders whether Google DNS is resistant to the attacks reported by Dan Kaminsky last year, where common DNS implementations relied on poor random numbers. H. D. Moore has forwarded Kerner some graphs he made from sampling Google DNS for randomness. First, a plot on port scanning

image and then a plot of source ports against transactions IDs


In both cases the graphs look quite random, and so both Kerner and Moore conclude that Google seems to be a right track here. But Moore concedes that more testing to be done.

November Blog Round-Up

I normally don’t post monthly blog summaries, but  last month there seemed to be quite a bit to write about. It was a good month for visits and page views, so thank you to everyone. Here is the No Tricks dashboard from Google Analytics (click to enlarge).


And a review of the posts

Opinion and Analysis



Improving Blog Navigation

Wednesday, December 2, 2009

Google Maps and Crypto Laws Mashup

Simon Hunt, VP at McAfee, has a great Google map mashup application that visually maps crypto laws to countries around the world, including individual US states. The map was last updated in September.