From the course: Symmetric Cryptography Essential Training

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CFB: Cipher feedback

CFB: Cipher feedback

From the course: Symmetric Cryptography Essential Training

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CFB: Cipher feedback

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- [Instructor] Cipher feedback mode, or CFB mode, converts a block cipher into something that behaves a lot like a stream cipher. It produces something like a key stream, but a block at a time rather than a byte at a time. Instead of encrypting the plaintext with the block cipher, the plaintext is combined with the results of encrypting the initialization vector. Then, the input to the next block is the ciphertext from the previous block, thus cipher feedback. If I stare at it long enough, I think that CFB looks a bit like cipher block chaining run backwards. Go back to that video and see if you agree. And here's the process for decryption. The block cipher encrypts the initialization vector with the key and the output of that is XOR-ed with the ciphertext to produce the message block. Block ciphers in CFB mode turn into a sort of self-synchronizing stream cipher. This means that if even a single byte of ciphertext is corrupted, it corrupts only the current plaintext block, but not…

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