diff --git a/src/LetsEncrypt/Entities/LetsEncrypt/State.cs b/src/LetsEncrypt/Entities/LetsEncrypt/State.cs
index d55db08..3f40e84 100644
--- a/src/LetsEncrypt/Entities/LetsEncrypt/State.cs
+++ b/src/LetsEncrypt/Entities/LetsEncrypt/State.cs
@@ -1,5 +1,7 @@
-using MaksIT.LetsEncrypt.Models.Responses;
+using MaksIT.Core.Security.JWK;
+using MaksIT.LetsEncrypt.Models.Responses;
 using MaksIT.LetsEncrypt.Services;
+using System.Security.Cryptography;
 
 
 namespace MaksIT.LetsEncrypt.Entities.LetsEncrypt;
@@ -12,4 +14,9 @@ public class State {
   public List<AuthorizationChallengeChallenge> Challenges { get; } = new List<AuthorizationChallengeChallenge>();
   public string? Nonce { get; set; }
   public RegistrationCache? Cache { get; set; }
+
+
+
+  public Jwk? Jwk;
+  private RSA? RSA;
 }
diff --git a/src/LetsEncrypt/Services/JwsService.cs b/src/LetsEncrypt/Services/JwsService.cs
index 97fdfb9..58d8069 100644
--- a/src/LetsEncrypt/Services/JwsService.cs
+++ b/src/LetsEncrypt/Services/JwsService.cs
@@ -26,12 +26,12 @@ public class JwsService : IJwsService {
   private RSA _rsa;
 
   public JwsService(RSA rsa) {
-    _rsa = rsa ?? throw new ArgumentNullException(nameof(rsa));
+    _rsa = rsa;
 
     var publicParameters = rsa.ExportParameters(false);
 
-    var exp = publicParameters.Exponent ?? throw new ArgumentNullException(nameof(publicParameters.Exponent));
-    var mod = publicParameters.Modulus ?? throw new ArgumentNullException(nameof(publicParameters.Modulus));
+    var exp = publicParameters.Exponent;
+    var mod = publicParameters.Modulus;
 
     _jwk = new Jwk() {
       KeyType = JwkKeyType.Rsa.Name,
@@ -80,6 +80,11 @@ public class JwsService : IJwsService {
   public string GetKeyAuthorization(string token) =>
     $"{token}.{GetSha256Thumbprint()}";
 
+
+  /// <summary>
+  /// For thumbprint calculation, always build the JSON string manually or use an anonymous object with the correct property order
+  /// </summary>
+  /// <returns></returns>
   private string GetSha256Thumbprint() {
 
     var thumbprint = new {
@@ -88,7 +93,7 @@ public class JwsService : IJwsService {
       n = _jwk.RsaModulus
     };
 
-    var json = "{\"e\":\"" + _jwk.RsaExponent + "\",\"kty\":\"RSA\",\"n\":\"" + _jwk.RsaModulus + "\"}";
+    var json = thumbprint.ToJson();
     return Base64UrlUtility.Encode(SHA256.HashData(Encoding.UTF8.GetBytes(json)));
   }
 }