tag: § Cryptography
OFB is a block cipher mode of operation which makes a block cipher into a synchronous stream cipher. OFB does not require padding.
Because of symmetry of Xor, the decryption algorithm is exactly the same as encryption.
Xor encrypted IV with the block of ciphertext.
The stream of encrypted IVs (keystream) can be computed beforehand and applied in parallel.
The keystream can be obtained by using CBC with a constant stream of zeros as input. That is useful as it allows using hardware acceleration.