Substitute numbers for letters (same letter, same number; different letters, different numbers) so the following equation works out:
KISS × KISS = PASSION
By trial and error the range is 1022 (for the result to be PASSION - 7 numbers) to 3155 (for the result to be PASSION - 7 numbers)
There is no need to try every combination... as this is a square, there's a pattern at how the answers are derived....
therefore 2033 x 2033 = 4133089
KISS x KISS = PASSION