Okay, I had a look at the instructions you are following. First, an observation: the assertion that not using a passphrase for an ssh-key is "not such good security" is generally false, as long as the private part of the key is safe (note the private half is never transmitted anywhere, due to the magic of public/private key pairs; it is just used by the local ssh process). Using a passphrase does not increase the security of the exchange at all, a key-pair with a passphrase is 100% exactly the same as one without, in terms of the ssh connection. The passphrase just makes the private key harder to use, should someone acquire it (eg, if they have physical access to your box, or have hacked into it somehow).
In the context of a number of pi's physically linked together, anyone who gains access to one will gain access to the others, so IMO in this context using a passphrase for keys used to log from one to the other is a tad silly. Nuff said. My point is don't be too concerned at this point about whether or not you are using a passphrase, you can change this later.
Also (this may simplify your life at some point), if you are using a passphrase, you can use something called ssh-agent such that you do not have to enter it all the time locally if you keep logging in and out of somewhere with the same key.
Anywho, stepping thru the superpi instructions: you've added your key to the other one as per #33. Then, as per #34 you have verified the key is there. There might be a complication here since you said you re-generated the key multiple times, and
cat >> .ssh/authorized_keys will add to authorized_keys everytime. This is sort of ok, except it makes it hard to tell if the last key you added, actually got added (which once you've added one it will be prompting you for a passphrase from an existing key if you use that method to add another -- which make it sort of not ok). If at all possible, I recommend you:
- Get rid of all the keys you've generated so far. As in remove everything in ~/.ssh on both pi's.
- Create a new key-pair (with or w/o passphrase) on the first pi.
- Copy the id_rsa.pub half and rename the copy "authorized_keys" (no suffix), and move that into
~/.ssh/ on the other pi using a means that you are certain of, eg, by putting it right on the SD card. You could use the superpi instructions recommended method, but do not do keep doing it over and over. Which is probably why it is just easier to copy it onto the card or use some other such direct method, since you don't have 63 more pi's to do anyway ;).
That's it for the ssh keys. You can test this by trying to ssh in to the other pi:
Nothing else. There should be a little blurb including "Your last login was...". You are now at a login prompt on the other pi. It will look the same otherwise since the filesystem images are identical. Type
exit to log out.
WRT step #36, which I presume is where you are having a problem, make sure you aren't still logged into the other one and try it. If you still have the same problem -- well, ditch the passphrase if it helps. It should not make any difference, although it could be that the python program you are referring to is actually not using the second pi at all (do you have a way to tell?) -- that would be confusing...