What is a Yubikey, I asked:
"Your YubiKey provides a second factor of security for your logins, beyond a username and password. Your YubiKey needs to be registered or paired with each computer, service, or site you use it with. "
"Your YubiKey provides a second factor of security for your logins, beyond a username and password. Your YubiKey needs to be registered or paired with each computer, service, or site you use it with. "
I do like the idea of being able to plug in to authenticate for ssh on any computer, however...
I genuinely want to understand this so I'm hoping you or someone else can explain.
Yubikey's and the like are a high target item, but probably only for government-level adversaries, in general you have to be pretty well funded to attack these things, plus their attack surface is very very small, and most all of the attack surface is physical (i.e. you have to physically get the yubikey device to attempt any hacks on it). These devices generally only have a USB port, so to get at them remotely you have to first get remote access to the device(computer) they are plugged into, making it even harder of a target.
That's the general overview. Specifically, SMS received tokens are not secure (because of the SMS part not being secure). NIST recently declared SMS based 2FA to be a bad idea, for instance.
If someone can remotely root your phone, they can remotely retrieve your shared secret, and thus generate your authentication tokens.
The only thing TOTP protects against is somebody collecting logins and using them later. Today good phishers do attacks JIT, so TOTP is pretty useless for that attack vector (and that is the most importent one).
Your Yubikey can pretty much be connected to your computer all the time. So usability is actually better.
Plus there is of course the problem of smartphone security.
https://www.wired.com/2016/06/hey-stop-using-texts-two-facto...
Other comments expalain the vulnerbility of phones, but Linode's Time-based One-time Password implementation (tied to a phone app) may have been hacked server-side.
http://www.securityweek.com/how-attackers-likely-bypassed-li...
- Clicking button is far easier and faster (it really does make a difference).
- Your smartphone is complex software and often attacked. Secrets can be stolen.
- Based on public-key crypto, no secret on the server.
- Built in phishing protection
- Your own private key is secure hardware that you can't read the key from
To be fair, a smartphone could also implement U2F and you would get some of the same benefits. Samsung phones for example already support UAF (the other FIDO) protocol.
It's not really possible to verify randomness this way - particularly for a device that already has a decent chunk of storage and crypto operahtions. Suppose the "random" number generator is actually an AES keystream coming from a key controlled by the NSA - how would you tell?
Everyone of us has asked that question before :)
Open to contributions as well!
I believe this adds protection against phishing because the browser communicates which origin (that is, which domain name) is sending the challenge, and that gets hashed into the signed response. So if trust-me-im-google.com proxies google.com, it can ask you for a one-time password, and the one-time password will be valid when google.com gets it, so the MITM can get your login cookie. But if you're using U2F, the signed response will say "Yes, I would like to authenticate to trust-me-im-google.com", and google.com will reject that.
[1] describes the flow at a high level, and [2] goes into more details
[1]: https://www.yubico.com/about/background/fido/
[2]: https://developers.yubico.com/U2F/Protocol_details/Overview....
https://developers.yubico.com/U2F/
Yubico has some python code here:
https://github.com/Yubico/python-u2flib-host
https://github.com/Yubico/python-u2flib-server
Chrome builds U2F into the browser itself for website authentication.
Another choice that looks (sadly, for me) more popular: https://github.com/ashtuchkin/u2f
A yubikey 4 or Neo has 2 slots which can be configured for about 5 different things. OTP, challenge response, static password, and some other things I can't remember right now. It also has 3 slots for a PGP private key, signing key, and encryption key. It also has 4 PIV slots to use as smart card key storage for authentication (ssh), code signing, and other things I can't remember. Then there are additional PIV slots to hold expired keys you might want to keep around for some reason?
It has quite a lot of functionality for a little device. The main difference between Neo and 4 is Neo has NFC, where 4 supports 4096 pgp keys. 4 is the newer one, but nothing new has NFC yet.
I use it with luks for full disk encryption, ssh, and to store my pgp key for QTPass/Android Password Store. QTPass + passff extension for firefox is nice.
I haven't set it up as a 2FA for sudo yet, but that's possible also. I don't plan to use it for PGP encrypted email for the same reasons described here.