Tuesday, June 12, 2007
I don’t know about you guys and gals but sometimes in life you do something or believe something that is completely logical but totally flawed. You may have noticed that there is a little yellow padlock icon in the corner of the screen that indicates that your online use of a credit card is secure from prying eyes because of what is called RSA encryption. That security is based on the idea that no one can calculate the large composite number behind the encryption. The composite number is based on two prime numbers about 150 to 200 digits long being multiplied together. Primes are defined as any number that can only be divided evenly by itself and 1. That is the only way you can absolutely determine if a prime is a prime. A prime does, however, if it is actually a prime, end in 1, 3, 7 or 9 in the first column. For instance 11, 13, 17 and 19 are all primes because they can’t be divided evenly by any of the numbers that precede them. Therefore, if you are going to break the composite code you only need to worry about seeing if probable prime numbers multiplied together and ending in 1, 3, 7, or 9 are actually primes. To add to the fun, if you multiply two prime numbers together creating a composite number which is obviously not a prime number its’ last column digit on the right will end in 1, 3, 7, or 9. Therefore you will know which one column prime number was multiplied together to create that first column digit. You may not know what the rest of the numbers were but you have a beginning. For instance prime 11 times prime 13 = 143 which is your composite number. If a composite number ends in 3 you can only produce a 3 if the unknown numbers that you are multiplying end in 1, 3, or 7, 9 because 1 X 3 = 3 and 7 X 9 = 63 ( 3 being the first column digit ). You can reverse engineer those numbers from the composite 143. Definitely OOP’s here!!!!