(1 point) A block cipher with encryption function e when used in OFB mode produces a keystream of pseudo-random blocks s1,s2,s3, where s1=e(IV) and si+1=e(si). These blocks are then used as a stream cipher to yield ciphertexts yi=sixi where xi is the i th block of plaintext. What would happen if, by coincidence, s3=s20. Would this threaten the security of the system? How?.