ljesh wrote:
I have one question.. can the first 12 letter be changed by any mean?
I mean this ones (touch on my yubikey)
cccccccccccchktrrtjfjrtcfrflgjirleccltjjtkhd
So the first 12 ones. Can they be changed in any way?
Yes, they can - you can change them into anything you like, given that you only use modhex characters (cbdefghijklnrtuv). However, this requires you to reprogram your key. By reprogramming your key, you will have to overwrite the AES secret in the key and hence you will render the key useless for use with the Yubico authentication server.
If you want to program your own key AND use the Yubico authentication servers, you'll need to choose a 12 letter identity string (the first 12) that begins with the sequence 'vv' (for example vvcbdefhjijk) and upload the AES secret you choose to the Yubico authentication server. It may well happen that the identity already was used by someone else, so be prepared to have to give it a few tries. Also, it is not guaranteed that Yubico will offer this service in the future.