[Cryptography] Secure universal message addressing

[Ángel González]

On 2016-04-05 at 18:46 +0200, Ralf Senderek wrote:
> 
> On Tue, 5 Apr 2016, John Gilmore wrote:
> 
> > 
> > The key idea here is a bad idea.
> > 
> > ssh public key authentication has this problem too.  Its default is
> > to assume that you want to use your same local identification to
> > identify you to every remote site that you try to access.  What a
> > clueless idea.  Luckily, ssh has survived despite this.  If you
> > avoid its whole public-key-per-user aspect, you can use it reliably
> > with usernames and passwords, different on every site.
> Or a different public-key per server, all you have to add is a switch
> "-i differentprivatekey" to your ssh command (and disable password
> access altogether on the server).
> 
>     --ralf

The best way is to remove your keys from the default locations and
configure them in ~/.ssh/config:

Host host1.example.com
  User john
  IdentityFile /path/to/key-host1
  IdentitiesOnly yes


Host host2.example.org
  User jdoe
  IdentityFile /path/to/key-host2
 
IdentitiesOnly yes

...and so on


NB that without IdentitiesOnly, the keys on your agent are tested
before the one provided in the config file or command line.