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Comment by jerf | Hacker News Reader

For practical purposes, that counts as "in the clear". Password should not be encrypted, they should be irreversibly hashed. (Preferably with bcrypt or scrypt or something meant for this use case; in this case I mean "hash" just in the technical sense of "irreversible", not that any ol' hash function is fine.)

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For login purposes, it is indeed good to use hashes, this prevents timing attacks and the like. But I fail to see the harm in keeping encrypted passwords for admin purposes. It is very helpful in certain situations.

Where do you keep the decryption key?

If it's stored in the same place as the encrypted password, then you have gained no security over storing it in plain text.

If it's stored in a separate system, then you have substantially increased the complexity of the system, and in general, a more complex system is harder to implement securely.

If the server is hacked, the attacker can decrypt everything. Your users are going to have a lot of problems, and you'll have lost (rightfully) their faith in your service.

Even if only the database is compromised it is still worth trying to find the key to decrypt all passwords whereas cracking a salted 10000 rounds of scypt or bcrypt hash is just not feasible unless you're the NSA on the hunt for Edward Snowden

Even stipulating perfectly correct use of encryption libraries to encrypt passwords (which is, in practice, an enormous stipulation on its own), there is a significant correlation between having enough access to obtain encrypted passwords, and having enough access to obtain the decryption keys and routines. Yes, there are breaks where the hacker can only get one or the other, but that's such a tenuous "security measure" that it's hardly worthy of the term.

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