val stringToInts = fn : string -> int list
val intsToString = fn : int list -> string
val pack = fn : int list * int * int -> int list
val unpack = fn : int list * int -> int list
val modPow = fn : int * int * int -> int
val encrypt = fn : string * int * int * int * int -> int list
val decrypt = fn : int list * int * int * int -> string