HmacSha256.cs

using System.Security.Cryptography;
using System.Text;
using Waher.Content;
 
namespace Waher.Security.JWS
{
    public class HmacSha256 : HmacSha
    {
        private HMACSHA256 hmacSHA256;
 
        public HmacSha256()
        {
            using (RandomNumberGenerator Rnd = RandomNumberGenerator.Create())
            {
                byte[] Secret = new byte[32];
                Rnd.GetBytes(Secret);
 
                this.Init(Secret);
            }
        }
 
        public HmacSha256(byte[] Secret)
        {
            this.Init(Secret);
        }
 
        private void Init(byte[] Secret)
        {
            this.hmacSHA256 = new HMACSHA256(Secret);
        }
 
        public override void Dispose()
        {
            if (!(this.hmacSHA256 is null))
            {
                this.hmacSHA256.Dispose();
                this.hmacSHA256 = null;
            }
        }
 
        public override string Name => "HS256";
 
        public override string Sign(string HeaderEncoded, string PayloadEncoded)
        {
            byte[] SignatureBin;
            string Token = HeaderEncoded + "." + PayloadEncoded;
            byte[] TokenBin = Encoding.ASCII.GetBytes(Token);
 
            lock (this.hmacSHA256)
            {
                SignatureBin = this.hmacSHA256.ComputeHash(TokenBin);
            }
 
            return Base64Url.Encode(SignatureBin);
        }
    }
}