Ever wondered what the difference between a block cipher and a stream cipher was? A block cipher has to be encrypted in chunks that are the block size for the cipher. For example, AES has block size of 16 bytes. So if you`re encrypting a bunch of small, 2 or 3 byte, chucks back and forth, over 80% of the data is useless padding, decreasing the speed of the encryption/decryption process and needlessly wasting network bandwidth to boot. So basically block ciphers are designed for large chucks of data, have block sizes requiring padding, and use a fixed, unvarying transformation.
Stream ciphers work well for large or small chucks of data. They`re suitable for smaller data sizes because no block size is required. And if speed is a concern, stream ciphers are your answer, because they use a simpler transformation that typically involves an xor`d keystream. So if you need to stream media, encrypt various data sizes including small ones, or have a need for a fast cipher then stream ciphers are your best bet.
SSL uses RC4 as the default stream cipher. It`s a pretty good one, though it`s getting a little older. There are some interesting advancements being made in the field and nearly two years ago wolfSSL added two ciphers from the eStream project into the code base, RABBIT and HC-128. RABBIT is nearly twice as fast as RC4 and HC-128 is about 5 times as fast! So if you`ve ever decided not to use SSL because of speed concerns, using wolfSSL`s stream ciphers should lessen or eliminate that performance doubt.
Both RABBIT and HC-128 are built by default into wolfSSL. Please see the examples or the docs for usage.