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§Scrambled Letters and Hash
The forward transformations are straightforward. The trickiest reverse transformation is the rotation based on the index of the letter. First we build a lookup table of how many places to rotate right based on the letter index. This is +1 for positions 0-3 and +2 for positions 4-7.
Then we invert this by mapping the transformed index to the rotation. For example position 3 is rotated right by 4 places, ending up at position 7, so the inverse lookup table to rotate left stores 4 at index 7.