Assuming this uses RSA for symmetric keys, offering "4096 bit keys to ensure the highest level of security." is a rather off-putting statement. The amount of bits of security offered by 4096-bit (Around 140 bits) keys over 2048-bit (112 bits) ones is negligible. You would be better off using ECDSA for security, offering up to 517 bits of security.
You wrote this app but didn't want to spend more than $1 on a domain? I would think about that, it is probably not to late to change.