Assume a kind of block cipher operates in the following ways. It works on 4-bit blocks, written as hexadecimal digits. For one particular key K, it implements the following encryption:

m 0 1 2 3 4 5 6 7 8 9 a b c d e f
EK(m) 8 4 c 2 7 f a 1 d 3 5 0 e 9 b 6

In the table, m is plaintext, EK(m) is the ciphertext given the particular key K. For example, if one input plaintext block is 4, then the ciphertext block after encryption is 7.

Using this key K, encrypt the following three plaintexts according to the indicated modes of operation. If an initialization vector (IV) or nonce is needed, please use IV/Nonce = 8.

ECB: 81b9

CBC: 2a9f

OFB: 63c0