 An earlier scrambler used in Packet over SONET/SDH (,) had a short polynomial with only 7 bits of internal state which allowed a malicious attacker to create a Denial-of-service attack by transmitting patterns in all 27−1 states, one of which was guaranteed to de-synchronize the clock recovery circuits.This vulnerability was kept secret until the scrambler length was increased to 43 bits (, ) making it impossible for a malicious attacker to jam the system with a short sequence.64b/66b avoided this vulnerability by using a scrambling polynomial with enough random internal state (58 bits) so that a dedicated attacker using a crafted Ethernet packet can only create a 64-bit run-length in the scrambler output once in about 29 years.