Bob needs to send a message to Alice and will use AES with one of the five different modes of operation (ECB, CBC, CFB, OFB, CTR). Bob and Alice have already secretly agreed on a key and (if needed) an initialization vector. If the mode of operation allows for advance computations, Alice has plenty of time to do these computations using the key and initialization vector before any ciphertext arrives from Bob. For each of the 5 modes, write a short paragraph that includes the following:

Describe what computations (if any) can be done in advance. Given the advance computations, describe the relative complexity (i.e. speed of computation) for the required computations needed to complete the decryption after the ciphertext is received by Alice. Discuss the need (or not) for padding.