Our Efforts on Cracking 40-bit DES
Demonstration only, not optimized.
Check first 4 bytes of “decrypted” message against a set of known “headers” for conformance, “yes” means highly probable that message is cracked.
Use idle times of about 50 workstations in the Department (most more than 3 years old), about 80% of key space searched in about 15 days.