chars = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"; data =
 IntegerDigits[
  FromDigits[
   StringPosition[chars, #][[1]] - 1 & /@ Characters[InputString[]],
   58], 256, 25];
data[[-4 ;;]] ==
 IntegerDigits[
   Hash[FromCharacterCode[
     IntegerDigits[Hash[FromCharacterCode[data[[;; -5]]], "SHA256"],
      256, 32]], "SHA256"], 256, 32][[;; 4]]