Simplify the following text for a Grade 8 native English-speaking person.
Original: In 1996 , Serge Vaudenay found a known-plaintext attack requiring 28r + 1 known plaintexts to break , where r is the number of rounds .
Simplified: In 1996 , Serge Vaudenay found a known-plaintext attack needing 28r + 1 known plaintexts to break , where r is the number of rounds .