RSA Security is a security company that protects government documents and also provides security software for online transactions that involve vital information (i.e. credit card numbers). Their encryption technique uses numbers that contain tens of millions of digits. Their 512-bit encryption takes eight months to crack, and by then, the code will probably have been changed. The only way to crack their codes is to factor the immense numbers that their programs generate.
Let's take a look at their encryption scheme:
P = prime number
Q = prime number
N = product of two prime numbers
The product of the two primes gives you a non-prime number. RSA specializes in providing large prime numbers for this equation so that the number is so large that only their software can factor it in a feasible amount of time.
N = P * Q
K = (P-1)(Q-1)
Now, pick any random number, and find its multiplicative inverse. Mod K it to get E.
E = D-1 mod K
Then assign any number you want to any letter that you want
B : H
C = encrypted form of B
C = Be
In order to break this encryption, you would need D, which means you need K, which means that you would have to factor it out, which would take a very long time. For more information, click on the link below to go to the RSA Security homepage.