>ok, I get a string of 16 characters of lenght how can get the 16 pairs of hexadecimal numbers? example "16ABCEE8FDD2A79AEBFB5B59419DDB83"
Those are the hexadecimal numbers. Hexadecimal numbers have 16 different digits instead of 10. This requires six additional "digits" - so the digits used are 0...9 and A...F ("A" = 10, "B" = 11, ... "F" = 15).
Each hex digit represents 4 bits. A pair of hex digits represents a byte.
HTH,
Hilmar.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)