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6. (20 points) Why do we need to use encryption modes? (a) Suppose you observed two ciphertexts a = e(+1) encrypted using a Electronic Codebook (ECB) encryption mode, what information does this leak about the plaintext? (b) Suppose you observed two ciphertexts a = (+) encrypted using a Cipher Block Chaining (CBC) encryption mode, what information does this leak about the plaintext