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Cryptography is the writing of secrets. The word 'cryptography' comes from the Greek 'cryptos', secret, and 'graphos', writing.

'''Cryptography''' is the writing of secrets. The word 'cryptography' comes from the Greek 'cryptos', secret, and 'graphos', writing.

All of cryptography (debatable since the dawn of quantum cryptography) can be described as one of two methods.

All of cryptography (debatable since the dawn of quantum cryptography) can be described as one of two methods.

Codes also include methods of hiding a message within a seemingly normal message (used frequently by POW's). A famous example of this is the [http://www.flickr.com/photos/8443340@N06/sets/72157600242068267/ September 1992 edition of Autocar]

Codes also include methods of hiding a message within a seemingly normal message (used frequently by POW's). A famous example of this is the [http://www.flickr.com/photos/8443340@N06/sets/72157600242068267/ September 1992 edition of Autocar]

James May amused himself while compiling a top 100 list of the cars that year arranged the capitalised letters across many pages to spell out "So, you think it's really good yeah? You should try making the bloody thing up. It's a real pain in the arse" (punctuation and spaces added for clarity)

James May amused himself while compiling a top 100 list of the cars that year arranged the capitalised letters across many pages to spell out "So, you think it's really good yeah? You should try making the bloody thing up. It's a real pain in the arse" (punctuation and spaces added for clarity).

Of course there is a very obvious problem with codes, find out the rules governing what is substituted for what and an intercepted message can be read easily. And in order to produce any useful codesets, large "dictionaries" were required by both sender and reciever.

Of course there is a very obvious problem with codes, find out the rules governing what is substituted for what and an intercepted message can be read easily. And in order to produce any useful codesets, large "dictionaries" were required by both sender and receiver.

Currently the most common form of cryptography is public key encryption. This relies on the fact that it takes significantly (order 10⁸ times) longer to find two prime factors of 1000 or more digit numbers than it does to multiply the numbers together to create the 1000 digit number in the first place.

Currently the most common form of cryptography is public key encryption. This relies on the fact that it takes significantly (order 10⁸ times) longer to find two prime factors of 1000 or more digit numbers than it does to multiply the numbers together to create the 1000 digit number in the first place.

In this system there are two keys, the first is the "private key", which only the '''recipient''' knows. The second is the "public key" which can be sent freely to anyone, allowing them to encrypt messages with it such that only the owner of the private key can decrypt them. These public keys are calculated from the private keys, but as they are often over 1000 digits long and would take many decades to calculate the private key from them (RSA, the most commonly used encryption protocol uses 2048 digit numbers which would take over 4000 years to crack with a desktop computer)

In this system there are two keys, the first is the "private key", which only the '''recipient''' knows. The second is the "public key" which can be sent freely to anyone, allowing them to encrypt messages with it such that only the owner of the private key can decrypt them. These public keys are calculated from the private keys, but as they are often over 1000 digits long and would take many decades to calculate the private key from them (RSA, the most commonly used encryption protocol uses 2048 digit numbers which would take over 4000 years to crack with a desktop computer).

This technology is put to use mostly on the internet. It allows sensitive data, eg. credit card numbers, phone numbers, social security numbers etc. to be transmitted without fear of interception and use by malevolent third parties. All internet banking and shopping uses this technology (whenever you see "https://" instead of "http://" in the address bar a public key algorithm is in use, most likely RSA"  

This technology is put to use mostly on the internet. It allows sensitive data, eg. credit card numbers, phone numbers, social security numbers etc. to be transmitted without fear of interception and use by malevolent third parties. All internet banking and shopping uses this technology (whenever you see "https://" instead of "http://" in the address bar a public key algorithm is in use, most likely RSA".

[[category:information technology]]

[[category:information technology]]