/sci/ - Science & Math

Any anon want to explain encryption simply?

>>5664191
define:encryption
encoding: the activity of converting data or information into code.

To get a basic grasp, take a look at caesar's cipher(very likely on wikipedia)

Imagine you and a friend both have a sheet of the same 1000 random letters. Then you can write a message, make a copy adding each corresponding letter from the sheet, and send it to your friend. Your friend will then subtract the letters from his sheet, yielding the original message.

A very simple form of computer encryption could simply use some algorithm that would start from a key to generate the sequence of random letters.

Other forms do all sorts of fancy things I don't really understand though.

>>5664168
Honestly, "The Code Book" is quite good for a layman reading.

take each letter/symbol in the alphabet and make it a number between 0 and 255
write it in binary
put the end to end so they are one big number
!important! add 9 or so random bits to the front !important!
pick two big ass primes p&q so that pq is bigger than the big number in step 3-4 could ever be
pick a number e such that the gcd of (p-1)(q-1) and e is just 1
when doing that you can find a d such that ed mod (p-1)(q-1) is 1
e and pq is the encrypt key
d and (p-1)(q-1) is the decrypt key

to encrypt the message, calculate c=m^e mod pq
to decrypt it, calculate m=c^d mod pq

The reason why it works is Lagrange's theorem and babies first group theory

I aprreciate the explanations but tbh, if someone asked me what encryption was I wouldnt be able to tell them.
/sci/ give the me an example of encryption that even your downs OP can understand...

>>5664305
encryption doesn't get more simple than this

>>5664305
You put child porn into a locked box and throw away the key
Mail it to Anonymous
Anonymous remembers the shape of the key from meeting you before and makes a new one
???
Profit!

>>5664309
Then why is there jobs just for finding which symbol means the letter "A" and what not? Surely cryptographers do more than that...

>>5664319
Very complex math goes into it. The better the encryption the harder the math

>>5664319
I think he was pointing out the base definition in a simple visual. Naturally there are more methods, layers, and theories to apply.

>>5664324
well the hard math is more in terms of how to generate the numbers, not what to do with them

>>5664319
He gave a very simple example. Caesar shifts are trivial to understand and were used thousands of years before computers existed. Some cyphers were developed that were more complicated and required some time for people to decode. With computers available, we can actually use cyphers that require doing arithmetic operations on numbers with several hundred digits, which is something you definitely don't want to do by hand.

The most very very basic its-not-how-it-really-works idea I can give you is the following. We've already seen how to make a cypher that replaces each letter with another letter. Imagine for the sake of simplicity that the English alphabet contains only 5 letters, A, B, C, D and E. There would then be 4 "Caesar shifts":

- The one that shifts by 1, so that A->B, B->C, C->D, D->E and E->A.
- The one that shifts by 2, so that A->C, B->D, C->E, D->A and E->B.
- The one that shifts by 3, so that A->D, B->E, C->A, D->B and E->C.
- The one that shifts by 4, so that A->E, B->A, C->B, D->C and E->D.

If you receive a coded message, you only have 4 cyphers to test to find the good one. Furthermore, if A is very very common compared to B, C, D and E, you can just look at the most common letter and figure out the cypher directly (if C is very common is the cyphered text, A->C).

Now, let's assume that instead of coding letter per letter, you code per pair of letters. There are 5*5=25 pairs of letters, so there are 24 possible shifts. The one that starts with AA->AB, the one that starts with AA->AC, etc until the one that starts with AA->EE.

You now have to test up to 24 cyphers to figure out which one is used. Also, you cannot look at common letters anymore. You have to look at common pairs of letters if you want to find out something.

If you consider letters grouped by 1000 instead of grouping by 2, then there are 5^1000-1 cyphers (huge number, cannot be brute-forced at all).

(...)

>>5664344
(...)

Furthermore, to do something like analyzing the frequent sequences of 1000 letters is impossible. There are too many possible sequences of 1000 letters, you cannot just list their frequencies and expect to see something meaningful. Moreover, unless you had a cyphered text of incredibly huge size, you wouldn't be able to compute meaningful empirical frequencies either.

Therefore, encoding by very large portions rather than letter by letter makes the encryption far more secure, even though it also makes it very hard to do by hand.

>>5664344
>>5664355
Anon delivers, thanks and I see now why its hard to explain simply. I will read up on this since this interest me a lot. Have a good one /sci/

>>5664195
Encoding is not encryption, but encryption is a type of encoding.

Encryption is a transformation of data such that only trusted parties are able to reverse the transformed data back into the original data.

Encoding is any reversible transformation of data.

>>5664393
if you type "define:encryption" into google, it returns what he posted.

>>5664380
For a really simple and easy-to-grasp type of binary encryption, look up "one-time pad."

Basically all modern symmetric encryption is an attempt to emulate a one-time pad, which is the only proven unbreakable form of encryption. The problem is that the secret key needs to be the same size as the data that you are encrypting, which makes telling someone what the key is a little difficult.

>>5664395
Interesting. It looks like google is getting the definition for WordNet at Princeton, which lists encryption as a synonym of encoding.

I just emailed WordNet suggesting they review the definitions.

>>5664408
Well, the "common" meaning of the terms are the same because people use "code" and "cypher" the same way. The definitions only differ when used in a mathematical context.

It's one example of terms that come from mathematics, but are not necessarily used properly by non-mathematicians (and those are the guys that write dictionaries).