diff --git a/103120/schema/json/ts_103120_Core.schema.json b/103120/schema/json/ts_103120_Core.schema.json
index 3216b8c746ba68d4087c259fc35a651c33d301d6..69a7f7aa0f558803484a688c0ab1659d4807bc52 100644
--- a/103120/schema/json/ts_103120_Core.schema.json
+++ b/103120/schema/json/ts_103120_Core.schema.json
@@ -14,6 +14,32 @@
         "Payload": {
           "$ref": "#/$defs/MessagePayload"
         },
+        "Signatures": {
+          "type": "array",
+          "minItems": 1,
+          "items": {
+            "type": "object",
+              "properties": {
+                "hash_algorithm": {
+                  "type": "string"
+                },
+                "algorithm": {
+                  "type": "string"
+                },
+                "public_key": {
+                  "type": "string"
+                },
+                "value": {
+                  "type": "string"
+                }
+              },
+              "required": [
+                "hash_algorithm",
+                "algorithm",
+                "value"
+              ]
+            }
+          },
         "Signature": {
           "properties": {
             "protected": {
@@ -29,6 +55,44 @@
           ]
         }
       },
+      "oneOf": [
+        {
+          "required": [
+            "Signatures"
+          ],
+          "not": {
+            "required": [
+              "Signature"
+            ]
+          }
+        },
+        {
+          "required": [
+            "Signature"
+          ],
+          "not": {
+            "required": [
+              "Signatures"
+            ]
+          }
+        },
+        {
+          "not": {
+            "anyOf": [
+              {
+                "required": [
+                  "Signatures"
+                ]
+              },
+              {
+                "required": [
+                  "Signature"
+                ]
+              }
+            ]
+          }
+        }
+      ],
       "required": [
         "Header",
         "Payload"