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I would like to get Mobile-phone verification or something else besides the SSH-key verification.

How can you add defence to the SSH-keys?

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closed as unclear what you're asking by Grant, HopelessN00b, Scott Pack, Tom O'Connor Feb 10 at 0:18

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What do you mean that someone is spoofing you? –  Michael Hampton Feb 9 at 7:54

3 Answers 3

up vote 5 down vote accepted

You can use Two Factor Authentication to improve the security of ssh keys (and other authentication methods). I use Duo's two factor authentication. It's free for a limited number of users and is relatively cheap beyond that. It can be installed in a wide variety of OS/Applications etc. There are other 2FA products available.

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I found that hardware two-factor tokens work well. I chose the yubikey, because it was reasonably inexpensive, had no licensing costs over and above the initial hardware purchase, required no specialist client-side software except a USB port, and I was entirely responsible for key management and distribution; I had to reposit my trust in noone except myself.

You can find a more detailed writeup here, if you want the technical nitty-gritty. (Disclaimer: I have no connection to yubico at all, save as a satisfied customer.)

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Maybe adding a one-time passcode authentication PAM (ex. https://code.google.com/p/google-authenticator/) to your system will give you some extra "layer of security".

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