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Prime and Composite Numbers

Only two factors or more than two factors

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Prime Protection

Credit: Game Developers Conference
Source: http://www.flickr.com/photos/officialgdc/6235163921/
License: CC BY-NC 3.0

Computers are everywhere, and the world of electronic commerce, or “e-commerce,” is a booming industry. What is e-commerce? Put very simply, e-commerce is the world of online shopping. Many people today do a lot of their shopping online, which means that computers and credit cards interface daily.

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Every time someone makes a purchase online that involves a credit card, prime and composite numbers are involved in the transaction. How exactly? Well, the computer uses a code to recognize a person’s credit card. Before the buyer's credit card information is sent through cyberspace, it is encrypted to protect it from being stolen by a computer hacker. To make sense of the encrypted information, a key to the code is required. One of the most popular methods of encryption makes use of prime and composite numbers.

Credit: Julien Gong Mien
Source: http://www.flickr.com/photos/bfishadow/7257134076/
License: CC BY-NC 3.0

Remember that a prime number is only divisible by itself and the number one, and that you get a composite number when you multiply two prime numbers together. Encryption codes can be created by multiplying two prime numbers together. The composite number is recognized by the computer, but only the bank knows the two original prime numbers. The composite numbers used as codes are usually extremely large. Because there are an unknown number of prime numbers, it is nearly impossible to break down the composite number into its two prime factors. Without the two primes, a hacker can’t access the credit card information.

See for yourself: http://www.slate.com/articles/health_and_science/science/2013/06/online_credit_card_security_the_rsa_algorithm_prime_numbers_and_pierre_fermat.html

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Below are few websites where you can practice working with prime and composite numbers.




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  1. [1]^ Credit: Game Developers Conference; Source: http://www.flickr.com/photos/officialgdc/6235163921/; License: CC BY-NC 3.0
  2. [2]^ Credit: Julien Gong Mien; Source: http://www.flickr.com/photos/bfishadow/7257134076/; License: CC BY-NC 3.0

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