That error message is most likely coming from the "
OpenVPN Connect" app on your phone or tablet. If that's the case, the error usually means that the size of the
RSA encryption key that you selected before generating the OpenVPN certs & keys is below the
2048 bits that is now the recommended minimum size.
Essentially, there are 2 possible solutions:
1) On the "
OpenVPN Connect" app, go to "
Settings ->
Advanced Settings" and change the "
Security Level" option from "
Preferred (Recommended)" to "
Legacy" which will allow the
1024-bit RSA encryption key used by your current OpenVPN certs & keys.
2) On the router WebGUI, go to "
VPN ->
VPN Server ->
OpenVPN" to regenerate the certs & keys *
after* changing the
RSA key size from 1024 to
2048 bits.
To be able to see & select a new RSA key size, toggle
OFF (i.e. DISABLE) the desired server instance (
1 or
2), and then toggle it back
ON (i.e. ENABLE), select the
2048-bit size (which should now be visible); now click on the "
Apply" button at the bottom of the page. Once this is completed, you will need to click on "
Renew" to regenerate the certs & keys, and then "
Export" to get the new client configuration file which you will need to re-import on all your client devices that use the server.
P.S.
Take a look at the following post which started a discussion about the same error:
The current firmware is using OpenSSL 1.1.1, which already ends support in September 2023. This means that it is no longer possible to get public security updates since last month. I still remember that it took about a year to migrate from OpenSSL 1.0.2 to 1.1.1 in 2019. I know there's so much...
www.snbforums.com
HTH