๐Ÿ“Cipher Feedback (CFB)

tags
ยง Cryptography
  • CFB is a block cipher mode of operation and is a close relative to CBC.
  • CFB make a block cipher into a self-synchronizing stream cipher.

    • CFB can self-synchronize if multiple of block size is lost.
    • If you need to allow dropping bits or bytes, you need to encrypt one bit or byte at a time (CFB can be combined with shift registers to do that).
  • CFB does not require padding.
  • Encryption algorithm:

    • IV is encrypted and xored with the plaintext.
    • The resulting ciphertext is the IV for the next block.
  • Decryption algorithm:

    • IV is encrypted and xored with the ciphertext.
    • Ciphertext is used as IV for the next block.

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