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Cryptography - First steps
Theoretical mumbjo jumbo
I'm going propose right now that there are two principles to all cryptography:
- Key production
- Algorithmic reliability
In plain English: the two main problems we encounter when trying to safely[1] encrypt a set of data, or more generally/simply, a thing is producing some kind of key that can't be reliably guess + an algorithm which can doesn't subject itself to being breakable[2].
Ciphers
All ciphers work on one principle: replacement of characters/things in the thing we are trying to cipher.
Some popular forms of this
What is Rotational ciphering
Let's take abc and increase each character by x=2.
We end up with cde.
I'm a malware developer how do I cipher binary data?
Easy, your alphabet isn't a-z or A-Z but now 0x00 - 0xff or, if you want to use pairs of bytes your alphabet is 0x0000 - 0xffff.
Again apply the same logic from above to the new "alphabet".
What are Substitution Ciphers
Let's shuffle our normal everyday alphabet from abcde... to uwfcj....
Now we take these two :
abcde...
uwfcj...
We can now say that all the a's in our thing that we want to cipher gets replaced by u's, b by w and so forth to the end.
That's perfect let's always use that!
Except you can use some statistical magic[3] to analyze the frequency of the ciphered letters and make a better guess at what the message might be. Also with a small character set there would be less to fuddle through, also keep in mind that cpu's operate in orders of billions of operations a second which means you character set needs to be comically large to ensure a processor doesn't reverse the cipher in seconds/minutes.
Encryption
hold up isn't cipher a form of encryption?
Yes&no. No because ciphers operate in-place as they are all just replacing things with other things, usually of the same length/shape/whatever.
Where is the distinction?
We now take our key and data/thing and produce a new seemingly unrelated encrypted thing.
So abc thrown through some encryption might turn into 234123j4h1 for whatever algorithmic reason(mileage may vary depending on algorithm).
What is Symmetric & asymmetric key encryption?
Conceptual answers:
Symmetric: One key to encrypt/decrypt or lock/unlock the thing, just a like a typical lock on a door.
Asymmetric: One key can encrypt/lock the thing(public) and one can open it(private key). The keynote here however is that the private key should be really hard to guess.