It has been shown in 2012 that you need at least 17 digits to uniquely specify a Sudoku puzzle: http://www.math.ie/McGuire_V1.pdf http://www.math.ie/McGuire_V1.

It has been shown in 2012 that you need at least 17 digits to uniquely specify a Sudoku puzzle: http://www.math.ie/McGuire_V1.pdf http://www.math.ie/McGuire_V1.pdf Their approach was quite close to solving every sudoku puzzle, although they traversed the space by the solutions.