Merge pull request #16 from trustoverip/ask/checksum

added integrity field in did document specification

spec.md

@@ -71,6 +71,7 @@ document. Adherence to the subsequent guidelines is mandatory:
     - `profile`: A JSON Profile document that can be resolved through HTTPS. Further requisites are detailed in the "Profile Document" section.
     - `definition`: If provided, this signifies the resolvable URI attribute
       enmeshed within the DID document. The corresponding definition is required to comply with the specifications delineated in the subsequent profile document section.
+    - An `integrity` property MAY be added as an aid in integrity protection and verification of the Profile document. It MUST be in the format of a  MultiHash, `<hash-func-type><digest-length><digest-value>` encoded as a varint and defined here [Multiformat](https://multiformats.io/multihash/). 
 
 An array of structs is not valid.
 
@@ -90,7 +91,8 @@ This following is an portion from the DID Document.
     "type": "TrustRegistry", 
     "serviceEndpoint": {
         "profile": "https://trustoverip.org/profiles/trp/v2",
-        "uri": "https://my-tr-service/"
+        "uri": "https://my-tr-service/",
+        "integrity: "122041dd7b6443542e75701aa98a0c235951a28a0d851b11564d20022ab11d2589a8",
     }
   }]
 }
@@ -317,4 +319,5 @@ provides clarity on the profile's purpose and its role within the DID ecosystem.
 - DID Core: https://www.w3.org/TR/did-core/ - Referenced mainly the DID Core spec.
 - DIDComm Messaging:  https://identity.foundation/didcomm-messaging/spec/ - used
   for understanding how to update the service endpoint of the DID Document.
+- [MultiHash](https://multiformats.io/multihash/): Used for integrity field.
 - https://www.w3.org/TR/vc-data-model/ : For the securtiy considerations and guidance on the profile document structure.