Refactor: Improve readability, documentation, and timing-attack resistance

- Added detailed comments explaining function behavior and security considerations
- Ensured timing-attack resistance by maintaining full loop execution
- Used local variables to store string lengths for better readability
- Replaced `while` loop with `for` for improved clarity
- Removed unnecessary pre-declared variable `i`
- Preserved use of `volatile` to prevent unwanted compiler optimizations
- Renamed variables for clearer meaning
- Cleaned up code structure for better maintainability
- Preserved original algorithm and performance characteristics