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## Coventry University

Skip to 0 minutes and 15 seconds As long as there has been written language there has been a desire to communicate in secret. In fact the ancient Greek word ‘cryptography’ translates as hidden writing. The desire to conceal a message’s content is as apparent today as it was in the early years of civilisation. Around 4000 years ago the spoken word physically manifested in the form of written language. In ancient Egypt hieroglyphs were scribed to include some partial substitutions of lesser-known symbols certain to a specific order but we’re unsure why. In Messapotamia around 1500 BC, similar examples of the partial substitution of characters is observed in cuneiform proto-writing; impressions on clay tablets.

Skip to 1 minute and 13 seconds Within these texts elementary forms of substitution, message integrity and authentication have been observed to conceal a message’s true meaning. As cuneiform gave way to the rise of the modern alphabet, Hebrew scribes developed a mono-alphabetic substitution cipher known as Atbash. Around about 500 to 600 BC. The process used a reverse alphabet to encrypt text by substituting A for Z and B for Y and so on and so on. As this method employed a direct substitution it was largely unsecure as there was no requirement for a key to be used to decipher the substituted text.

Skip to 2 minutes and 8 seconds In the fifth century BC the ancient Greeks produce the tool known as a scytale, a hexagonal staff wound by a long leather strip upon which a message was written. Unraveled, the message would form a seemingly random string of characters allowing the message to only be decrypted by the recipient if they were in possession of a staff with the same dimensions as the original used to encrypt the message. Re-binding the scytale would then revealed the content of the original message. This could have been the first known use of a key within cryptography.

Skip to 2 minutes and 52 seconds Suetonius’s collection of biographies called The Lives of the Twelve Caesar’s was published around AD 121 and this gives a clear description of the use of a cipher, which we now refer to as the Caesar cipher. This was created around 50 to 60 BC. The cipher shifted the letters of the alphabet by a fixed designation to encode the text. Caesar’s preferred substitution was by a factor of 3 shifting A to D and B to E until the end of the alphabet where XYZ would then become A,B and C, for instance. This process was actually less strong than the Atbash cipher but being that very few people were literate the time it was probably good enough for their needs.

Skip to 3 minutes and 43 seconds In India between the first and fourth centuries AD Vatsayana’s Karma Sutra identified cryptography as the 44th and 45th of the 64 arts that men and women should study.

Skip to 3 minutes and 58 seconds From this list the 44th and the 45th arts read: ‘The art of understanding writing in cipher and the writing of words in a peculiar way. The art of speaking by changing the

Skip to 4 minutes and 11 seconds forms of words, it is of various kinds: some speak by changing the beginning and end of words, others by adding unnecessary letters between every syllable of a word’ and so on. The Kama Sutra does not give the methods for cipher writing and the exact date that the Kama Sutra was written is unknown but is often cited between the first and the fourth century AD. In many circumstances the motives for hiding messages is unclear. It might be a boast or conceit of the scribe. It might be a protection of mysteries from part of the population or it might be in respect of military secrets or business and legal communication or perhaps underground and illicit correspondence.

Skip to 5 minutes and 0 seconds Whatever the motivation, it is clear that has always been a strong cryptographic presence in communications throughout history.

# Codes and ciphers in early history

Cryptography is the story of keeping information secret, but it has always been driven by the need to thwart those who want to reveal the secrets.

Here we examine the algorithms used by early cryptographers, from some of the earliest recorded codes to the ciphers of 15th century intrigue.

Cryptography has been one of the ways people throughout history have met the need for secrecy in communication. Some of the methods were trivial, relying as much on the illiteracy of the majority than any serious attempt to hide the message, but others stood up to analysis for a long time before finally being broken.

You may wish to read the article in the See also section at the end of this step on 10 of the most mysterious codes and ciphers in history.