Block Ciphers: ECB

Example of using ECB: Suppose that your plaintext is: 010 110, which are two blocks of 3 bits each. Also, suppose that you are given the following encryption function E(b) as a table:

Plaintext	000	001	010	011	100	101	110	111
Ciphertext	101	010	000	001	111	100	011	110

• To encrypt the plaintext, you'll plug each block into the function, separately, to get the ciphertext block.
  • In our case, we do: E(010) = 000, and E(110) = 011, so our ciphertext is: 000 011.
• To decrypt the ciphertext, solve for the block variable b by looking back at the table as follows: E(b) = 000 ⇒ b = 010 and E(b) = 011 ⇒ b = 110, so we got our plaintext 010 110 back.

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Fun Class Activity: Use the encryption table E(b) to (a) encrypt the blocks: 101 100 (b) decrypt the blocks: 001 010.