University of Cambridge Develops Potentially More Secure Password Storage System

An anonymous reader writes "University of Cambridge's S-CRIB Scrambler resides in a Raspberry Pi and performs a hash-based message authentication code (HMAC). 'The secret 10-character key used to generate the HMAC resides solely on the dongle. Because it's not included in password tables that are stored on servers, the key could remain secret even in the event of a major security breach.' There are pros and cons associated with this method, of course, ranging from scalability to loss of access due to device hardware failure. As with all current options for password security, there's no guarantee that even this system remains secure."

Comments

Usefulness is reduces if a single account is known

[gnoshi]

As was pointed out by someone on Ars, even if the secret key used by this device isn't stolen it can be bruteforced by having a single known account on the system. This is not a trivial problem, because it seems that they are using SHA1 (on the basis that the key can never be stolen, so the hashes don't need to be so strong). As such, there is a mountain of good gear out there for running lots and lots of hashes fast.

Basically:
1. Create account/password with online retailer
2. Steal user database for online retailer
3. Find you own account, for which you know the username and password (and salt, because it is in the database) and associated hash
4. Bruteforce the HMAC key required to get the stored hash using your username, password and salt
5. Use that same universal HMAC key for attacking all the other accounts
6. profit?

This assumes that there is a single key used for the HMAC and stored on the dongle, but it seems that is actually the case.
It does make getting all the passwords a bit harder, but it isn't a miracle cure.

Makes sense

[swillden]

This isn't by any means a new concept; systems that care deeply about security have been using host security module (HSM)-based keyed hashing for decades. But doing it in an inexpensive, readily-available device is a really good idea for systems that don't need the physical security features offered by HSMs -- and that's nearly all systems. The key is to make sure that the communications channel between host and dongle cannot be used to compromise the dongle. Ideally, you should just ensure that the dongle system will not -- under any circumstances -- respond to anything other than hashing requests, and that codepath should be carefully validated for security bugs.

Re:Usefulness is reduces if a single account is kn

[Bengie]

10 random chars are good for 65bits. Log(92^10)/Log(2) = 65.24

because it's a cheap, easy, fun proof of concept

[raymorris]

You wouldn't use an RPi in production, of course. x86 would be just as silly. A $3 hardware encryption chip attached to most any microcontroller would be several thousand times faster and an order of magnitude cheaper than x86. x86 is for general purpose computing - this is a single purpose device.

So why did they use a raspberry pi? Probably because they already had one, or several, already knew how to use it, and could put the code together in an hour or so to demonstrate the concept and have a little fun doing it.