What is RSA ?
RSA stands for Rivest-Shamir-Adleman. It is widely used for asymmetric encryption algorithm in cryptography.
RSA has two components, one is public key and the other one is private key. You can safely distribute the public key to anyone and use the private key for decryption.
Good part with RSA is security. It is based on large numbers so that it is not easily possible to decrypt. RSA is widely used on the internet for securing the communication for the applications like emails, digital signatures and so on.
In our application, you can select different key sizes like 512, 1024, 2048. Of course higher the key size, the better the security is but it affects the size of the file. It will be completely up to the person how (s)he wants to set up her/his system.