`sig
class type rng =
object
method random_bytes : bytes -> int -> int -> unit
method wipe : unit
end
val string : Cryptokit.Random.rng -> int -> string
val secure_rng : Cryptokit.Random.rng
val system_rng : unit -> Cryptokit.Random.rng
val device_rng : string -> Cryptokit.Random.rng
val egd_rng : string -> Cryptokit.Random.rng
val hardware_rng : unit -> Cryptokit.Random.rng
val pseudo_rng : string -> Cryptokit.Random.rng
val pseudo_rng_aes_ctr : string -> Cryptokit.Random.rng
end`