Example of encryption key pair algorithm?

[CosmicVoyager]

Greetings,

I know that when encrypting something with the public key of a key pair, the encrypted data can only be decrypted with the private key of the pair. And it can not be decrypted with the public key that was just used.

I do not understand how it is possible to perform a mathematical operation on a number, but then not be able to reverse the operation to get the original value.

How is it that, knowing exactly what operations were performed, you can not undo them and get the original value?

Can someone give a very simple example of such an operation?

Thanks

 

[DrGreg]

You might try reading One-way function. A simple example: multiplying two prime numbers together is easy, but if you are given the product and asked to find the two prime factors it is very difficult (i.e. takes a long time) if the number is a very, very large one.