Cryptography Questions Medium
Output Feedback (OFB) mode is a mode of operation used in cryptography to encrypt and decrypt data. It is a synchronous stream cipher mode that converts a block cipher into a stream cipher.
In OFB mode, the encryption process involves generating a keystream by encrypting an initialization vector (IV) using the block cipher algorithm. The IV is then combined with the plaintext using a bitwise XOR operation to produce the ciphertext. The same process is repeated for each subsequent block of plaintext.
The key feature of OFB mode is that it does not require the encryption algorithm to be applied directly to the plaintext. Instead, it operates on the previous ciphertext block or the IV to generate the keystream. This makes OFB mode suitable for applications where random access to the encrypted data is required, as the encryption and decryption processes can be performed independently on any block of the data.
One advantage of OFB mode is that errors in the transmission or storage of the ciphertext do not propagate to subsequent blocks, as each block is encrypted independently. However, it is important to use a unique IV for each encryption session to ensure the security of the encryption.
Overall, OFB mode provides confidentiality and integrity of data by converting a block cipher into a stream cipher, allowing for efficient and secure encryption and decryption of data.