diff --git a/DysonNetwork.Sphere/ActivityPub/ActivityPubDeliveryService.cs b/DysonNetwork.Sphere/ActivityPub/ActivityPubDeliveryService.cs
index c58aa58..b1e1433 100644
--- a/DysonNetwork.Sphere/ActivityPub/ActivityPubDeliveryService.cs
+++ b/DysonNetwork.Sphere/ActivityPub/ActivityPubDeliveryService.cs
@@ -1,5 +1,6 @@
 using DysonNetwork.Shared.Models;
 using Microsoft.EntityFrameworkCore;
+using System.Security.Cryptography;
 using System.Text;
 using System.Text.Json;
 
@@ -235,6 +236,12 @@ public class ActivityPubDeliveryService(
             request.Content = new StringContent(json, Encoding.UTF8, "application/activity+json");
             request.Headers.Date = DateTimeOffset.UtcNow;
             
+            var bodyBytes = Encoding.UTF8.GetBytes(json);
+            using var sha256 = SHA256.Create();
+            var hash = sha256.ComputeHash(bodyBytes);
+            var digest = $"SHA-256={Convert.ToBase64String(hash)}";
+            request.Headers.Add("Digest", digest);
+            
             var signatureHeaders = await signatureService.SignOutgoingRequest(request, actorUri);
             var signature = signatureHeaders;
             
diff --git a/DysonNetwork.Sphere/ActivityPub/ActivityPubSignatureService.cs b/DysonNetwork.Sphere/ActivityPub/ActivityPubSignatureService.cs
index 9af22fb..63c5cf7 100644
--- a/DysonNetwork.Sphere/ActivityPub/ActivityPubSignatureService.cs
+++ b/DysonNetwork.Sphere/ActivityPub/ActivityPubSignatureService.cs
@@ -82,7 +82,7 @@ public class ActivityPubSignatureService(
         var keyPair = GetOrGenerateKeyPair(publisher);
         var keyId = $"{actorUri}#main-key";
         
-        var headersToSign = new[] { "(request-target)", "host", "date" };
+        var headersToSign = new[] { "(request-target)", "host", "date", "digest" };
         var signingString = BuildSigningStringForRequest(request, headersToSign);
         var signature = keyService.Sign(keyPair.privateKeyPem, signingString);
         
@@ -223,6 +223,13 @@ public class ActivityPubSignatureService(
                     sb.Append(request.Headers.GetValues("Date").First());
                 }
             }
+            else if (header == "digest")
+            {
+                if (request.Headers.Contains("Digest"))
+                {
+                    sb.Append(request.Headers.GetValues("Digest").First());
+                }
+            }
         }
         
         return sb.ToString();