Hashing with SHA512 in C# (Salt + Pepper).

Hashing.cs

using System;
using System.Security.Cryptography;
using System.Text;

public class Hasher {
    private static readonly RandomNumberGenerator Rng = RandomNumberGenerator.Create();

    public string CreateHash(string input, byte[] salt, string pepper) {
        byte[] saltBytes;
        byte[] pepperBytes = Encoding.UTF8.GetBytes(pepper);

        if (salt != Array.Empty<byte>()) {
            saltBytes = salt;
        } else {
            int saltLength = 16;
            saltBytes = new byte[saltLength];
            Rng.GetNonZeroBytes(saltBytes);
            Rng.Dispose();
        }

        byte[] inputData = Encoding.UTF8.GetBytes(input);
        byte[] inputDataAndSalt = new byte[input.Length + saltBytes.Length];
        byte[] inputDataAndSaltAndPepper = new byte[input.Length + saltBytes.Length + pepperBytes.Length];
        byte[] hashValue = Array.Empty<byte>();

        HMACSHA512 sha512 = new();
        hashValue = sha512.ComputeHash(inputDataAndSaltAndPepper);
        sha512.Dispose();
        
        byte[] result = new byte[hashValue.Length + saltBytes.Length];

        for (var i = 0; i < hashValue.Length; i++) {
            result[i] = hashValue[i];
        }

        for (var i = 0; i < saltBytes.Length; i++) {
            result[hashValue.Length + i] = saltBytes[i];
        }
        
        return Convert.ToBase64String(result);
    }

    public bool ConfirmHash(string input, string confirmHashValue, string pepper) {
        byte[] confirmHashBytes = Convert.FromBase64String(confirmHashValue);

        var hashSize = 64;
        byte[] saltBytes = new byte[confirmHashBytes.Length - hashSize];

        for (var i = 0; i < saltBytes.Length; i++) {
            saltBytes[i] = confirmHashBytes[hashSize + 1];
        }

        string controlRehashValue = CreateHash(input, Array.Empty<byte>(), pepper);

        return confirmHashValue == controlRehashValue;
    }
}