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Generally speaking, cryptography has been the sole domain of governments. All governments of the world have a branch dedicated to the interception and decryption of encoded information. In [[America]], this is the [[CIA]]; in [[Britain]], it's [[MI5]]; in [[Vatican City]] it's [[Iscariot]] (Vatican Section XIII).

Generally speaking, cryptography has been the sole domain of governments. All governments of the world have a branch dedicated to the interception and decryption of encoded information. In [[America]], this is the [[CIA]]; in [[Britain]], it's [[MI5]]; in [[Vatican City]] it's [[Iscariot]] (Vatican Section XIII).

Cryptography has played a large part in many wars. In the [[World War I|First World War]], [[Mata Hari]] was responsible for carrying messages back and forth for the [[German]] government, causing the deaths of thousands of [[French]] soldiers.<ref>http://www.firstworldwar.com/bio/matahari.htm</ref> In the [[World War II|Second World War]], [[British]] soldiers captured the crew and The [[Enigma machine]] of German [[U-boat]] [[U-571]], leading to the decryption of [[Nazi]] communications and the end of the war.

Cryptography has played a large part in many wars. In the [[World War I|First World War]], [[Mata Hari]] was responsible for carrying messages back and forth for the [[German]] government, causing the deaths of thousands of [[French]] soldiers.<ref>http://www.firstworldwar.com/bio/matahari.htm</ref> In the [[World War II|Second World War]], [[British]] soldiers captured the crew and The [[Enigma machine]] of German [[U-boat]] [[U-571]], leading to the decryption of [[Nazi]] communications and the end of the war.

 

 

[[Ethel Rosenberg]] and [[Julius Rosenberg]] sold US atomic secrets to the [[USSR]] at the height of the [[Cold War]]. They were convicted and executed in the electric chair at [[Sing Sing]] prison.

== Modern Uses Of Cryptography ==

== Modern Uses Of Cryptography ==

The most common forms of cryptography in use today are [[symmetric key encryption]] and [[public key encryption]]. These cryptographic systems rely on hardness assumptions about certain computational problems, such as that it takes significantly longer (order 10⁸ times) 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.  Public-key cryptographic systems are typically slower than symmetric-key systems, and as a result slower public-key systems such as RSA are often used to generate a key for use in a faster symmetric-key system such as AES or DES.

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 public-key cryptography 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).

Cryptographic protocols are often used on the Internet. They allow sensitive data, e.g. 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 of your browser, an encryption algorithm is in use to protect information transmitted through that web page.

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 of your browser, an encryption algorithm is in use to protect information transmitted through that web page.

==References==

==References==