Folks, here is a new way, the web way of retrieving your AES keys here and now:
CheersBelow was the old way of doing it:
If you host your own Yubikey OTP validation server, you need to import your Yubikeys' secret AES keys into your validation server database. In order to get the AES keys, please send the following to Support@Yubico.com
 2 consecutive OTPs generated from each Yubikey as proof of possession.
 Your GPG (or PGP) public key so we can encrypt your AES keys to send to you. It looks like this:
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1.4.6 (GNU/Linux)
-----END PGP PUBLIC KEY BLOCK-----
*GPG is free to use. If you need help on GPG, here is a very well written and authoritative doc at:
 By default Yubico generates a CSV file with your keys. If you tell us which validation server you use, or what kind of SQL INSERT statement you want, Yubico can generate the SQL script for you to insert them all into your database in a snap.
Though we can still send you in plain text if you like but we suggest them encrypted by your public key, so no one else can decrypt and use your AES secrets.
Protect the secret after you got it. Since if stolen, someone can clone a Yubikey identical as yours.