Are there high-speed ciphers designed for things like internet
streams without sacrificing security? There are so many options
that operate in stream mode. How would one choose a cipher? By
default use AES. AES is a block cipher, i.e. a function which,
given a key, maps block values (of 128 bits, in the case of AES)
to other block values of the same size. To encrypt a message,
one must use the block cipher in a chaining mode which tells how
the input data should be split and encrypted and assembled
again. Almost all modes allow for streaming (encrypting a huge
message on the go, without having to store it entirely in RAM or
disk). The good modes combine encryption and integrity check,
see EAX and GCM. Among traditional encryption-only modes, the
current one is CBC, the newer being CTR; CTR has the advantage
of not requiring padding, because it encrypts a sequence of x
bytes into exactly x bytes, for all x, whereas CBC requires an
input with a length multiple of the block size. I have a 2.4 GHz
Core2 Intel CPU