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Standard encryption and steganography involve encoding or hiding messages using methods that are independent of the content the messages contain. This is normally the only viable option, especially in an internet situation where the communicating parties may have never met in person. However, this chapter would not be complete without mentioning that altering the meaning, rather than the form, of a message according to a pre-agreed code can also play an important role in keeping information secret.
During the Second World War, the U.S. military employed speakers of the Navajo language as a means of transmitting confidential messages. Scarcely known beyond the Navajo Nation at the time, the language offered a ready-made means of encryption. Essentially, its fiendishly complex grammar and pronunciation formed the encryption method and the correspondences between its vocabulary and English acted as a very long key. Because of the completely fixed nature of this key, communication experts within the U.S. army were initially somewhat sceptical of the whole idea.
In the event, however, the Japanese never managed to eavesdrop on the Navajo messages, which is more than can be said for several of the mathematically-based encoding mechanisms that were in use at the same time. Because their language did not contain equivalents for many of the military terms under discussion, the Navajo code talkers pre-agreed a 211-word code that consisted of Navajo circumlocutions for them. The Navajo for between waters meant Britain, the Navajo for iron hat meant Germany, and the Navajo for chicken hawk meant dive bomber. It is striking that, despite their tiny number, these specially invented words ended up playing a crucial role in keeping the Navajo messages impenetrable. They meant that even when the Japanese captured and tortured a native speaker of Navajo who was not a code talker, he was unable to make any sense of the messages.
In more recent years, one person who seems to have been successful in outwitting law-enforcement authorities with a meaning-based encoding scheme is none other than Bernardo Provenzano. Following his capture and arrest in 2006, he spent hours each day marking the Bible in his cell with cryptic signs and references that bore a close resemblance to annotations found in the Bible he had had with him when he was caught. Eventually, in 2008, the prison authorities cut off all contact between Provenzano and the outside world because they suspected he was using a code based on Bible annotations to run his criminal empire from behind bars.
Provenzano is thought to have switched to the Bible code in 2002 on realizing his Caesar cipher messages were being read. The FBI tried to crack the Bible code, but as far as we know they could not. We might presume this is because it was founded at least partially on pre-agreed meanings taken from the fabric of the Mafia subculture. On this occasion at least, Provenzano seems to have been successful in encoding his messages.
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