Host Key Verification Failed

Question

I'm trying to ssh into my UBUNTU through my PC with Cygwin on it. I can WINSCP without a hitch, however when I ssh through a command line it comes up with this error:

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@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
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IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
5d:84:de:4e:a8:81:df:22:06:23:98:34:cd:26:f5:1a.
Please contact your system administrator.
Add correct host key in /home/Trevor/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /home/DIRECTORY
ECDSA host key for HOSTNAME has changed and you have requested strict checking.
Host key verification failed.

So I looked it up and it said that I needed to change my host key in my .ssh folder that's located in my home folder. Well, there wasn't one so I made one. Tried again and got the same error.

What to do?

Answer 1

1. go to known_hosts vim ~/.ssh/known_hosts
2. delete the hostname that is causing this issue HOSTNAME

Answer 2

try

 rm -f /home/user/.ssh/known_hosts

or deletes the offending key from the known_hosts

ssh-keygen -R hostname

Answer 3

"Host key verification failed" means that the host key of the remote host was changed.

Ssh stores the host keys of the remote hosts in ~/.ssh/known_hosts. You can either edit that text file manually and remove the old key (you can see the line number in the error message), or use

ssh-keygen -R hostname

Answer 4

Tested in Mac and Ubuntu 16.04

ECDSA host key for HOSTNAME has changed and you have requested strict checking. Host key verification failed. means,

If you get this error message then the host you are trying to connect was connected before and possibly the EDSA key is now a mismatch. This typically happens when you are under the DHCP network and multiple devices are allocated with the same IP at different instances of time. As a result the there is a key mis-match i.e. the EDSA key is catched into your system for that hostname.

To get rid of this problem, the sophisticated way is to remove the entry from

vim ~/.ssh/known_host (you can use anything in place of vim)

delete the entire line which contains the hostname which is your pain point

hostname(192.168.1.123 for example) EDSA_key

It should work without restarting you system.

Not recommended

Otherwise the hard way around is by, removing all the contents of the file(truncating), never delete the file completely it may lead to some other problem and don't modify permission of the file also.

Answer 5

This generally means that the host key of your remote host has been changed. It can be used to avoid the men in the middle attacks and to make your host secure. You can simply remove this using:

ssh-keygen -R hostname | ip address 

or

ssh-keygen -f "/root/.ssh/known_hosts" -R ip address

Answer 6

So looks like your ubuntu host key changed since you ssh to it from Cygwin last time.

The message already told you what to do,

cd /home/Trevor.ssh 
open know_hosts file and delete the old key of your ubunto box 
once the key is removed, ssh to your ubuntu box again