Sha256 Hashes in F#

Here’s the translation of the SHA256 Hashes example from Go to F#:

Our first program demonstrates how to compute SHA256 hashes. SHA256 hashes are frequently used to compute short identities for binary or text blobs. For example, TLS/SSL certificates use SHA256 to compute a certificate’s signature. Here’s how to compute SHA256 hashes in F#.

open System
open System.Security.Cryptography
open System.Text

let computeSHA256 (input: string) =
    use sha256 = SHA256.Create()
    let inputBytes = Encoding.UTF8.GetBytes(input)
    let hashBytes = sha256.ComputeHash(inputBytes)
    BitConverter.ToString(hashBytes).Replace("-", "").ToLower()

[<EntryPoint>]
let main argv =
    let s = "sha256 this string"
    let hash = computeSHA256 s
    printfn "%s" s
    printfn "%s" hash
    0

F# implements several hash functions in the System.Security.Cryptography namespace.

Here we define a function computeSHA256 that takes a string input and returns its SHA256 hash as a lowercase hexadecimal string.

Inside the computeSHA256 function:

1. We create a new SHA256 hash object.
2. We convert the input string to a byte array.
3. We compute the hash of the byte array.
4. We convert the resulting byte array to a hexadecimal string and format it.

In the main function:

1. We define a string to be hashed.
2. We call our computeSHA256 function to compute the hash.
3. We print the original string and its hash.

Running the program computes the hash and prints it in a human-readable hex format.

$ dotnet run
sha256 this string
1af1dfa857bf1d8814fe1af8983c18080019922e557f15a8a...

You can compute other hashes using a similar pattern to the one shown above. For example, to compute SHA512 hashes, you would use SHA512.Create() instead of SHA256.Create().

Note that if you need cryptographically secure hashes, you should carefully research hash strength!