Do passwords matter?

You don’t have to look very hard to find an article discussing password breaches. Recently, there was a lot of buzz around LinkedIn, Last.fm, and eHarmony, three very large sites suffering from passwords being leaked to the public. This is not a new phenomenon (earlier this year everyone was all up in arms about the Zappos password breach), but one that continues to garner attention in the media.

However, what most journalists are saying about password breaches is likely different from what I am about to tell you – it simply does not matter how strong your password is, how it is encrypted when stored by the provider, or how the transport layer is encrypted (e.g., SSL). Here’s why:

How it’s encrypted matters, but no one does it right

Many websites today, primarily for performance reasons, are using traditional one-way hashing algorithms to store your passwords (such as MD5 or SHA1). This means you give the website a password, it computes a cryptographic hash and stores it in a database of some kind. The plaintext password should never be written to disk. The next time you login, the website computes the hash in the same manner and compares it to the value stored in the database.

This is all well and good, until someone obtains a copy of the password hashes. Obtaining the hashes, without any other protections, such as password salting, two or more users with the same password will have the same hash value. This allows attackers to generate very large databases of already-hashed passwords and make a comparison. Hardware on graphics processing units (GPU) can help accelerate the process.

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