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F# converting hmac python into f#

How would I convert this Python code into F# "

message = nonce + client_id + api_key
signature = hmac.new(API_SECRET, msg=message, digestmod=hashlib.sha256).hexdigest().upper()

My code so far to achieve this:

let message =string(nonce)+ client_id + api_key
let signature = HMACSHA256.Create(API_secret+message)

Simple issue is I cannot find what represents the hexdigest() function in F#.

Also, do I combine the API_Secret with the message as I have done or must they be separated?

Solution

  • I think you need somethink like this:

    let hexdigest (bytes : byte[]) =
   let sb = System.Text.StringBuilder()
   bytes |> Array.iter (fun b -> b.ToString("X2") |> sb.Append |> ignore)
   string sb

let signature =
   use hmac = new HMACSHA256.Create(API_secret)
   hmac.ComputeHash(message)
   |> hexdigest

    The part with the StringBuilder is what hexdigest does in python (if I get hexdigest right)