Stream vs. Block Ciphers

Stream Ciphers are typically bit-wise. They either have a very long key (that eventually repeats) or a reusable key that generates a repeatable but seemingly random string of bits. They perform some operation (typically an exclusive OR) with one of these key bits and one of the message bits.

Where might a stream cipher be good? Why might it be not so good?

Block Ciphers operate on a pre-determined block of bits (one byte, one word, 512 bytes, so forth), mixing key data in with the message data in a variety of different ways. Most of the algorithms you hear about (DES, 3DES, Blowfish, AES, etcetera) are block ciphers.

What might the uses and short-comings of a block cipher be?

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