is there cryptography algorithm space /input invariant? I'm searching for a cryptographic algorithm that produces the same result for the same input, and if in the input, at position k, there is XXXXXX, then in the output at position k there is always the field YYYYYY.
This isn't the most direct answer to your question, but you could segment your input into blocks, and just encrypt the blocks. However, performing this could possibly introduce vulnerabilities caused by being able to exploit how you're segmenting the data (if that method can't be stored in your brain).

Part of how a lot of encryption methods work is they can take a variable length input and create an output that varies size. The only encryption method I can think of that is input invariant the way you describe is a Caesar cipher.