RSA is a public-key encryption algorithm. The RSA algorithm used by the Xceed Encryption Library is based on the RSAES-OAEP scheme. RSAES-OAEP is short for "RSA Encryption Scheme - Optimal Asymmetric Encryption Padding". It is the encryption scheme recommended by RSA Security. It prevents a variety of known attacks against the original RSA, including the guessed plain text attack described here:
"An adversary intercepts a message, makes one or more attempts to guess the plain text data (before encryption) and encrypts each guess using the recipient's public key. If any of the resulting encrypted guesses match the intercepted message, the adversary then knows the message."
The RSA public-key encryption algorithm is much slower than most secret-key encryption algorithms, and therefore should be avoided when encrypting long streams of data because of the speed and the larger encrypted streams it produces. When possible, consider using the concept of a digital envelope instead.
For the curious, the exponent (known as the "e" value) used internally for the RSA key-generation algorithm is fixed at 17 and cannot be changed.