I feel like there must be a simple explanation, but I've been looking around haven't found any wholesome answers.
Take for example my name is Alice and my best friend Bob and we want to communicate securely.
If I write a program that takes my text and obscures it through several dozen filters and can successfully reverse the process, assuming I then wrote the program on a piece of paper and gave Bob my paper in the middle of the desert where he then memorized it and burned it, how would anyone ever possibly crack our code?
To elaborate on obscurity take for example I do the following:
- Take my original string and convert it to binary
- From there I add the last digit of the year to each number
- Then I reversed the text
- Then I added a randomly generated character once every 3 characters
- And so forth, on and on, until I had several dozens obscurities filtered through.
Why wouldn't it be more-or-less impossible to decrypt our message without the program or formula itself (or at least for several years)?
Side note: I would understand completely why security through obscurity wouldn't work for people saying things like "I'll just use weird OS and I'll be safe because who the hell understands weird OS!" I am asking purely asking about sending an encrypted message back and forth, that if intercepted by a third party would not be able to realistically crack due to its obscurity.