MorganS:
So, check if the code fits by looking at it. Does it assign any large buffers? How big are they?Program storage is unlikely to be the issue, so you don't need to know how may bytes the program itself takes, just its SRAM storage while it's running.
Yes it does assign large buffers, there is a large string i was provided which is used in generating the private key, around 400 character long.
Should i switch boards to arduino due instead? Or someone other board.
I dont have much knowledge regarding this so i need some help in deciding.
As mentioned in the earlier comments a 32 bit processor is required so i looked up DUE