StringHashing.cs

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

namespace DKNet.Fw.Extensions.Encryption;

/// <summary>
///     Provides string hashing utilities for common security operations.
/// </summary>
/// <remarks>
///     Purpose: To provide a set of utility methods for hashing strings.
///     Rationale: Ensures data integrity and security by providing hashing algorithms.
///     Functionality:
///     - Generates HMAC-SHA256 hashes with a specified key
///     - Generates SHA256 hashes
///     Integration:
///     - Can be used as an extension method for string manipulation
///     - Works with other encryption utilities in the framework
///     Best Practices:
///     - Use strong, randomly generated keys for HMAC-SHA256
///     - Store hashes securely, not the original data
///     - Use SHA256 for general-purpose hashing
///     - Validate input strings before hashing
/// </remarks>
public static class StringHashing
{
    /// <summary>
    ///     Generates an HMAC-SHA256 hash for the provided value using the specified key.
    /// </summary>
    /// <param name="value">The input string to be hashed.</param>
    /// <param name="key">The secret key used for hashing.</param>
    /// <returns>A hexadecimal string representing the HMAC-SHA256 hash of the input value.</returns>
    /// <exception cref="ArgumentException">Thrown when value is null or empty.</exception>
    public static string ToCmd5(this string value, string key)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(value);

        using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(key));
        var hash = hmac.ComputeHash(Encoding.UTF8.GetBytes(value));
        return BitConverter.ToString(hash).Replace("-", "").ToLowerInvariant();
    }

    /// <summary>
    ///     Generates a SHA256 hash for the provided value.
    /// </summary>
    /// <param name="value">The input string to be hashed.</param>
    /// <returns>A hexadecimal string representing the SHA256 hash of the input value.</returns>
    /// <exception cref="ArgumentException">Thrown when value is null or empty.</exception>
    public static string ToSha256(this string value)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(value);

        // Convert the input string to a byte array and compute the hash using SHA256.HashData
        var inputBytes = Encoding.UTF8.GetBytes(value);
        var hashBytes = SHA256.HashData(inputBytes);

        // Use built-in .NET framework method for hex conversion
        return BitConverter.ToString(hashBytes).Replace("-", "").ToLowerInvariant();
    }
}