Re: OT: Storing encryption keys securely

[Anonymous Monk]

Database encryption is largely meaningless because of this problem. Point-of-sale systems sometimes require a human to enter an encryption key to unlock them when they start up, but nobody wants to do that on the web. You might have the webserver switch to an unprivileged user so it can't get the password again after it starts up. If an attacker breaks root on your server, there's really no way to stop them.

Schneier described a way to address the password-in-memory problem in his book Applied Cryptography. He called it a "boojum"... unfortunately, I can't seem to find a good explanation of it online.

[BrowserUk]

Boojum is described here.

Essentially it consists of generating a random number, and xoring the secret data with that random number, and then storing both xored data and the random number in different places in memory. When the secret value is required, xoring the two back together recovers it; but the actual secret doesn't appear anywhere in memory.

It goes on to suggest generating a new random number and re-xoring once a second, and trying to ensure that both pieces of data are stored on different chips.