Do I need to change IV while encrypting multiple packets in CFB mode?

Question

Erlang crypto library has aes_cfb_ivecno function . Does this mean that the same IVecshould be used for several rounds? Or should you use encrypted data from the last step, as in the “DES in CBC mode” example at the end of the linked page?

Answer 1

IV MUST NOT be reused. Otherwise, two packets starting with the same n bytes will be encrypted into streams with the same n bytes. This is a serious security issue.

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