After updating my Asus WL-520gU router to the latest version of the Tomato firmware (with OpenVPN support), I ran into a strange error. While trying to access the admin interface via https:, I got the following error in my Firefox browser:
Cannot communicate securely with peer: no common encryption algorithm(s).
(Error code: ssl_error_no_cypher_overlap)
I couldn’t access via http: either (which was expected, as that’s how I’d set up the router with the prior FW version to enforce security).
Googling for the error didn’t turn up anything really useful. I at first thought that the update had somehow gone bad, but I was able to get out to the internet through the router so that brought some hope. I was also able to ssh in to the router so all seemed to be OK in general. Only problem was I couldn’t access the router’s controls.
On an off chance, I decided to check out the Firefox settings for SSL security. Under the Advanced tab, I tried turning off and on the SSL and TLS checkboxes. Nothing changed. Then I decided to delete/remove the Certificate entries for my router and try again. That turned out to be the trick. For some reason Firefox didn’t like the security certificate any more – this time I got the familiar “This connection is untrusted” (or effectively similar) warning and was able to accept the security exception for my self-signed SSL certificate once more and all was fine.
Just in case someone else runs into the same problem… try the above.