#Internet iceberg encryption mod
For example if y=25, x^y mod z doesn’t require us to do 24 multiplications of x, but can be calculated as x^16*x^8*x. given y, calculating x^y mod z takes a number of multiplications that grows with the log base 2 of y.given x^y mod z=res there is no known way (nowadays) to guess what y was knowing x, z and res other than trying to keep on multiplying x by itself until we find res.Their trick is to use a discrete exponent: x^y mod z, with z being prime with x so that we have the following properties: In the Diffie-Hellman key exchange both Alice and Bob create their own private key, say AK and BK, that they don’t share with each other. Here it comes: the Diffie-Hellman key exchange. If they send that key over the internet, an eavesdropper, Eve, could easily spoof it and be able to decrypt later any message they send to each other. The problem raised from secret key cryptography is that Alice and Bob must exchange the key used for the encryption before they starting communicating. The algorithms used nowadays (mainly AES, or Advanced Encryption System) are far more complex than the plain XOR function and decrypting a message would take hundreds of years to solve. Actually with the XOR function, though still being quite hard to do, it is possible to notice patterns and make guesses based on characters that are more common in the alphabet, for example. If we had a key of 8 bytes and split our message in 8 bytes chunks, we could encrypt it instantaneously, whereas an attacker would have to try 2^64 different possible keys. One intuitive example of a very simple symmetric encryption algorithm is the XOR function: The algorithm to encrypt and decrypt the messages is known, but the security is based on the fact that guessing the message from the encrypted message takes a huge computational effort. Secret key cryptographyīoth Alice and Bob own an identical key that is used to encrypt and decrypt messages that they send to each other. A one way function is a function f for which is easy to calculate f(x)=z but extremely hard guess what x was knowing f and z. The gist of all these different topics is the concept of a one way function.
#Internet iceberg encryption full
Let’s first list the main concepts that are needed to have a full end to end secure communication: It would be as if we were requested in a very crowded room to confidentially communicate with someone else on the other side of the room without having the other people guessing what we said.Īs an foreigner I am able to do that with my friends from home, but in general it’s a tough challenge, that unveils a fascinating topic: Cryptography. Nowadays via the internet we need to constantly communicate to people we don’t know, sending messages that can be constantly spoofed by other people. If you are asking yourself the same question, or need to convince your mom she can safely use her credit card online, here is brief summary of what’s going on behind the curtains. While going through a set of configurations to connect on a remote machine I was asked to upload my public key and I realized that I didn’t really know what that was for.
0 kommentar(er)
