“This cipher is considered one of the holy grails of cryptography, as at the time the cipher had resisted attacks for 50 years, so any attempts to find a solution were truly a moonshot.”
The Z340 resisted everyone for 50 years. A small team of amateurs cracked it in 2020, one of them stuck at home in Melbourne’s 112-day lockdown. They sent the solution to the FBI, which then confirmed it. Volunteers with laptops closed a puzzle the bureau never did.