output feedback

A block cipher mode that modifies ECB mode to operate on plaintext segments of variable length less than or equal to the block length. [FP081] (See: block cipher, [SP38A].)

Tutorial: This mode operates by directly using the algorithm's previously generated output block as the algorithm's next input block (i.e., by "feeding back" the output block) and combining (exclusive OR-ing) the output block with the next plaintext segment (of block length or less) to form the next ciphertext segment.