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How is a computer going to translate this?
It wont.
Because the encryption code cannot be guessed.
We're talking about two different things.
You're talking about closed algorithm encryption and I'm talking about open algorithm encryption.
When you encrypt something in SHA256 the algorithm that encrypted it is not a secret, only the key is.
It needs to be this way, because of the algorithm was also secret there would be no way for the other party to decrypt it even with a public key.
What you are describing (secret algorithm) codes require that the intended recipient has somehow secretly been given the algorithm. The algorithm is the key in this case.
The example of the enigma code was open algorithm because they had the machine. The nazis didn't try to give away the machine, but they knew damn well they would probably lose one. If they knew they would never lose the machine they hardly needed to try so hard with the coding.
BTW the terminology has changed a bit since 1940. I believe they referred to particular encryption algorithms as ciphers in the non-digital context.
A computer would have a tough time with secret ciphers (arbitrary algorithms). It would find it impossible to brute force a bunch of digits because there would be no way to know you've decrypted the message as opposed to seeing a bunch of normal human vocabulary appearing.
However, anything that can have its rules described can be written into a computer. I'm sure there are secret ciphers for digital encryption that utilize offsets and operators as Korea describes.
They are simply useless in the modern context because open algorithm encryption is so damn useful. -> It's incredibly helpful to be able to have receivers who can decrypt the message without forcing you to change your encryption method. When the algorithm is the key, every single reader becomes a potential impersonator.