Cracking PGP In the Cloud

pariax writes "So you wanna build your own massively distributed password cracking infrastructure? Electric Alchemy has published a writeup detailing their experiences cracking PGP ZIP archives using brute force computing power provided by Amazon EC2 and a distributed password cracker from Elcomsoft."

Comments

Bottom Line: Use Long, Unusual Passwords

[Constantin]

First of all, the article is a very nice summary of the issues involved with setting up a cloud to crack passwords - the nuts and bolts, if you will. I liked that the authors took the time to look into the economics of trying to crack passwords, how much money it would cost vs. how long it would take. Password cracking is one example of massively scalable computing, which is presumably why the NSA allegedly has had to keep upgrading the electrical infrastructure at their headquarters. Elcomsoft certainly made a splash with their PGP-cracking software and managing to harness the power of cheap GPU cards (which are set up for parallel processing) was a bit of genius. That said, even massive horsepower runs into a brick wall once the passphrases become long and the encryption algorithm is good.

On page 2 of the article, the authors nicely summarize the cost of cracking longer and longer passwords. Once passwords start incorporating special characters (per SPEC), the cost shoots sky high even for relatively short passwords (i.e. $10MM+ for a 9 character password, $1BN for a 10-character password, the US national debt for a 12-character password). The article so clearly lays out why the various law enforcement agencies have been focusing on being able to force folk to disclose their encryption keys. The cost of cracking a well-executed encryption scheme combined with a good password is simply too high. So, go ahead and use those special characters, upper and lowercase, etc. to make life interesting for would-be snoops. But realize that unless trends in privacy rights swing the other way, law enforcement will simply compel key disclosure, as they have for years in the UK, for example.

Lastly, the article underscores the value of keychain-type schemes that allow many long passphrases to be stored in a accessible format. Make it easy to have long, complex passphrases and it becomes more likely that people will actually use them.

Re:And tons of carbon enter the air

[maxwell demon]

The company surely did have the private PGP key lying around. They just forgot the password.

As an analogy, think of a safe. A good safe is hard to break in if you don't have the key. If you have the key, it's quite easy. Now you fear that someone could break in your house, get the key and open your safe. Therefore you put the key for the big safe into another, smaller safe. If you need to open the big safe, you first open the small safe, take out the key of the big safe and then open that.

Now if you have lost the key for the small safe, and the small safe is less secure than the big safe, you'll certainly not crack the big safe, but just the small safe in order to get the key of the big safe.

Now, the key for the small safe is your password, and the key of the big safe is the PGP key. If someone has access to the small safe (the password-protected PGP key), then the security of whatever is in the big safe is certainly limited by the security of the small safe.

Now with emails, the point is that the big safe (the encrypted email) is out in the public, while the small safe (the password-protected PGP key) is in your home (i.e. on your computer, which hopefully itself has appropriate protection against intruders).

So the security of your PGP encrypted mail is limited by the combination of the security of your computer and the security of your PGP password. If your computer is basically unprotected, and your PGP password is weak, then anyone can read your encrypted mail by simply breaking into your computer, copying the private PGP key, and breaking the password. If your computer is well-secured, the attacker will have a hard time to get your private PGP key, and if you PGP password is strong, the attacker will have a hard time to break it if he manages to get the PGP private key.