Checking my understanding of Public Key Encryption and question about size of algorithm implementations?

You got things right. The main problem caused by this scheme is "How can Bob be sure that the public key he got from "the world" is Alice's public key, and not Chuck's public key? Indeed, if it were Chuck's public key, Chuck would be able to decrypt the message Bob sends to Alice.

You got things right. The main problem caused by this scheme is "How can Bob be sure that the public key he got from "the world" is Alice's public key, and not Chuck's public key? Indeed, if it were Chuck's public key, Chuck would be able to decrypt the message Bob sends to Alice.

This is resolved by certificates. Every participant has a copy of the public key of well-known and trusted certificate authorities. When Alice want to publish it public key to the world, she pays one of these authorities to get a certificate, containing her public key.

When getting a certificate, everyone can verify, with the authority's public key, that the certificate hasn't been corrupted, and so be sure that the public key is Alice's public key, and not Chuck's. The basic process of certification is a cryptographic signature : the certificate authority encrypts some data with its private key. When you have the data, its signature, and the authority's public key, you may verify that decrypting the signature with the authority's public key leads to the original data.

RSA is a de facto standard, and is available in many languages and platforms. You shouldn't reimplement it yourself.

Thanks for the additional information about authentication. Oh I didn't want to implement it, I just wanted to know about how many lines it took the professional geniuses of the world to do it in :) – Pete May 26 at 14:22.

Yep that's pretty much it. Note that it is not completely correct to say that Chuck can't decrypt the message, but rather he can't do it easily with known mathematical methods. The reason for this is that the key generation algorithms rely on what are known as one-way functions.

These are functions that are relatively easy to compute for a given input, but very difficult to work back from the output. An example of a one way function is multiplying two large prime numbers together; the multiplication is easy, but finding the prime factors again is very difficult, barring some new mathematical breakthrough. As to the implementations of the methods, they vary depending on the exact encryption scheme being used.

One of the earlier and better known public key encryption schemes is RSA. There are detailed steps on all three of key generation, encryption, and decryption here.

Thanks for the link! I'm going to be reading for a while. – Pete May 26 at 14:23.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.