what problem happen if we always use IV Zero in CBC Mode?

Question

i have a question about CBC operating mode. what problem happen if we always use IV Zero in CBC Mode?

score 1 · Accepted Answer · answered Nov 15 '15 at 16:05

It become a deterministic encryption key: Same message encrypted twice, produces the same ciphertext. This has negative consequences on the security of the cipher, because an adversary know if you encrypt the same message, which means she can distinguish encryptions.

what problem happen if we always use IV Zero in CBC Mode?

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