Don't include base characters twice in hash

What I mean with "twice": The first 30 characters are copied _and_ included in the calculation of the last 20 characters. Changing a bit in the first 30 characters of an input string causes two changes in the result: one in the first 30 and one in the last 20 characters. What I expect instead: Two strings that share the same appendix should result in two hashes that also share the same appendix.

Use case: The order of
* `"a00000000000000000000000000000000000000000000000001"` and
* `"a00000000000000000000000000000000000000000000000002"` should be the same as the order of
* `"b00000000000000000000000000000000000000000000000001"` and
* `"b00000000000000000000000000000000000000000000000002"` (not necessary in ascending order, but the same order anyway).