Module 11 Flashcards
Encryption
-send a postcard of info through internet to get to destination but WHAT IF THERE IS AN EVIL DOER?
-it intercepts the information and can copy it and send it somewhere else as it is heading to its destination, so it will now have a copy of it
-to prevent this we ENCRYPT OUR MESSAGES
so the sender encrypts the message, and sends the encrypted message to the reciever, and now the evil doer cannot intercept because ti cannot/ does not have the instructions to decrypt the message
One technique to encrypt messages
+3 Caesar Cypher
-move the letters forward 3 in the encrypted message]
ie
original is abc
encrypted is def
the reciever needs to know the instructions (the number) so that they can decrypt it
Modern Encryption
use huge numbres to enceupt our messages, not just +3 like the ceasear cypher
AS LONG AS SENDER AND RECEIVER HAVE THE instrcutions to DECRYPT it will work smoothly
Why will we not have complete privacy
because of packets
-first contact we have to send info on internet is packets
-since we are sending the password too, we will never have COMPLETE privacy
0cant change it completely in secret unless we have KEY EXCHANGE!!!!!!!!!!
One way function
-easy to do in one direction but hard to do in the other
ex: have two prime numbers multiplied to equal a number, we know the final number and need to figure out what the og prime numbers were
ie (x)(y)=14
2*7
this is easy for computer but if its a really big number, the computer will take a little while to figure it out
another example:
MODULO REMAINDER
Modulo REmainder/ key exchange technique
example of one way function and a way to encrypt
1337/10=133 +7 (remainder)
written as 1337mod10=7
or 3^x mod17=2
this is hard for computer to do
use this to encrypt
the password will be something like 3^xmod17
-everyone will know this
even the evil doer
Sender picks a number and reciever picks a number and only we will know these numbers
-we calculate the mod equation with our chosen numbers and we will send eachother the remainder answer that everyone will know
but now we get those numbers and raise that to the number that we originally picked that no one knows, and we will get the same number as partner, look at ipad
no one can determine this other number adn that is the number we will use to encrypt message
Assymmetric keys
-another way to communicate on internet
-assymetric key is a two key system
IMAGINE A LOCK
-blue key turns it clockwise (public key)
-red key turns it counterclockwise (private key)
Public (blue key) can only lock information, cant unlock it unless u have a red key. SO ONE WAY FUNCTION FOR BLUE KEY
this allows thousands of blue keys to be sent out that can lock it but only one red key that u have can unlock it
this works for sending messages because all three ofus ( evil doer, sender adn reciever have blue key), but only i have red key, so the other person can send me a locked message (locked with blue key) and only i can open it up
How to verify a person with assymetric keys
If only i have a red key and i lock it, anyone can open it witha blue key, but the fact that i locked it with a red key and only i have that red key shows that it was me
-but someone can just say that it was them so we have someone else that we trust (a third party) that also verifies that this is actually the person (this communication is similar to other one way functions),
bascially we have people we trust adn if someone else vouches for them we will contiue to trust them
HTTPS
Secure Hypertext Transfer Protocol
-a protocol that establishes rules for communicating in a secure way
-if i want to verify that it is a safe website, i send the server a message saying i can communicate with X, if they can too, they can send me a certificate and a public blue key, i will check certificate witha third party to makesure its real
-once i do this, i will share a private key with the server and now we can commuincate
-individual message can have a mini-certificate or a specific “timestamp” to ensure that it has not been forged further.
ie if we go to certain websites, there will be a lock that indicates that this is a secure and private discussion adn there will also even be a certificate that indicates that this is a trusted thing that a thrid party signed off to
