Clues left in the clumsily encrypted notes of a Mafia don have helped Italian investigators to track his associates and ultimately contributed to his capture after years on the run.

The recently busted Bernardo Provenzano, reputed to be the "boss of bosses" of the Sicilian Mafia, used a modified form of the Caesar cipher to obscure "sensitive information" in notes left to either his family or underlings.

According to a biography (written by Italian journalists Salvo Palazzolo and Ernesto Oliva) on bernardoprovenzano.net, the content of these notes varied from meal requests to his family to orders to his lieutenants where numbers were used to disguise people's names.

Provenzano, 73, was arrested last week in a farm close to his home town of Corleone on the Italian island of Sicily after almost 40 years on the run. He's accused of numerous homicides including the 1992 murder of two judges, a crime that earned him a life sentence in absentia. Provenzano who earned the nickname Binnu u tratturi (Binnu the tractor) because of his rep for mowing down enemies, latterly took to writing instructions incorporating basic encryption on small scraps of paper, known locally as pizzini.

The classic Caesar cipher moves every letter in the alphabet three charecters later (so A becomes D and B becomes E, etc.). The so-called Binnu code assigns a number in order to each letter in the Italian alphabet and adds three to that number in the ciphertext so that "A" is 4, "B" is 5 and so on.

The code would have been more secure if the numerical shift applied to the ciphertext was varied from time to time. As it was, the contents of messages was readily deciphered. "Looks like kindergarten cryptography to me. It will keep your kid sister out, but it won't keep the police out. But what do you expect from someone who is computer illiterate?" security guru Bruce Schneier told Discovery News.

Provenzano left school aged only eight, a factor which might explain the simplistic nature of the way sensitive messages, normally typed out on old typewriters, were encoded. The decipherment of the pizzini sent and received by Provenzano allowed police to identify his associates and ultimately contributed to investigative efforts that led to Provenzano's arrest, Discovery News reports. ®