# RSA

Suppose Bob wishes to send a message *m* to Alice. He knows *N* and *e*, which Alice has announced. He turns *m* into a number *n* < *N*, using some previously agreed-upon
reversible protocol. For example, each character in a plaintext message could be converted to its ASCII code, and the codes concatenated into a single number. If necessary, he can break *m* into pieces and encrypt each piece separately.
He then computes the ciphertext *c*:

This can be done quickly using the method of exponentiation by squaring. Bob then transmits *c* to Alice.