Calculate the SHA-256 Digest of a File using cryptokit

Task

Cryptography / Calculate the SHA-256 Digest of a File

Opam Packages Used

• cryptokit Tested with version: 1.18 — Used libraries: cryptokit

Code

(* `sha256sum` computes the SHA-256 digest of the given file, and prints it in hexadecimal. *) let sha256sum filename = (* We select SHA-256 as the hash function *) let hash = Cryptokit.Hash.sha256 () in (* We open the given file in binary mode (no end-of-line translation), and pass `Cryptokit.hash_channel hash` to apply the SHA-256 hash function to the contents of the file. *) let digest = In_channel.with_open_bin filename (Cryptokit.hash_channel hash) in (* We convert the hash (32 bytes) to hexadecimal (64 hexadecimal digits) *) let hex_digest = Cryptokit.transform_string (Cryptokit.Hexa.encode ()) digest in (* We print the hexadecimal hash and the filename *) Printf.printf "%s %s\n" hex_digest filename (* The entry point for this program calls `sha256sum` on each filename passed as argument on the command line. *) let _ = for i = 1 to Array.length Sys.argv - 1 do sha256sum Sys.argv.(i) done

let sha256sum filename =

  let hash = Cryptokit.Hash.sha256 () in

  let digest =
    In_channel.with_open_bin filename
      (Cryptokit.hash_channel hash)
  in

  let hex_digest =
    Cryptokit.transform_string
      (Cryptokit.Hexa.encode ()) digest
  in

  Printf.printf "%s  %s\n" hex_digest filename

let _ =
  for i = 1 to Array.length Sys.argv - 1 do
    sha256sum Sys.argv.(i)
  done

Recipe not working? Comments not clear or out of date?