Post: Migrate existing passwords to bcrypt

This post amends [my bcrypt post][1]. [Redditor kcen commented][2] on my post, noting that my method "leaves you with a large set of known insecure passwords in your database". After talking it over with colleagues and consulting [a Cryptography Stack Exchange question][3], I realized he was right. This was further supported by [a Tweet from Geoffrey Couprie][4].

[1]: http://taylor.fausak.me/2013/05/08/upgrading-to-bcrypt/
[2]: http://www.reddit.com/r/rails/comments/1e049z/upgrading_to_bcrypt/c9vws08
[3]: http://crypto.stackexchange.com/questions/2945/is-this-password-migration-strategy-secure
[4]: https://twitter.com/gcouprie/status/335888084170338304