Logic Masters Deutschland e.V.

One of my all-time favorites in the Mystery Killer subgenre is German Whisper Cages by kolot. I started wondering if it's possible to create a sudoku with that ruleset without resorting to single-cell cages. It proved very hard indeed, but finally I succeeded (by developing further one of kolot's ideas).

Have fun solving!

Rules:

Normal sudoku rules apply. Digits cannot repeat within a cage. The totals of adjacent cages must differ by at least 5.

Play with SudokuPad

The puzzle might be quite hard to crack, but no bifurcations or long deduction chains are needed at any point. If you can't find the break-in, check the hints below (highlight white text to read):

Hint 1: To unlock the puzzle, you need two different keys.

Hint 2: One key is found among the smallest cages, the other among the largest.

Hint 3: The lock into which both keys fit is vertical and consists of three cells.

And here's yet another hint if you get stuck in the midgame:

Hint 4: The big ones are even stronger together.