If the router is covered by an active maintenance program so that you can download new code then upgrading the IOS is certainly possible. And the code that you are running 12.4(1c) is actually quite old.
There are two factors to consider when we look at what code is running and what code you might want to change to. The obvious factor is the version of code which is indicated in the numeric value (12.4(1c) or the recent 12.4(24)). The other factor is what is frequently referred to as Feature Set or in recent code may be called the licensing level. And this is the one that controls whether encryption is supported or not. You could upgrade to the new 12.4(24) and if you still use the IP Base without encryption then you still would not be able to generate RSA keys etc. And if you change to a feature set that does support encryption then you could generate RSA keys whether you were still at 12.4(1c) or at the new 12.4(24).
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...