Added protocol tags

proto/umbra/tagged_payload.proto

@@ -0,0 +1,14 @@
+syntax = "proto3";
+
+package umbra.tagged_payload;
+
+// Specification: "../../specs/protocol_tags.md"
+
+
+// This message allows bytes on the wire to be tagged with the associated specification/type
+message TaggedPayload {
+	uint32 domain = 1;
+	uint32 tag = 2;
+	bytes payload_bytes = 3;
+}
+

specs/protocol_tags.md

@@ -0,0 +1,97 @@
+---
+title: PROTOCOL_TAGS
+name: Payload tags in Multiprotocol Environments
+category: Standards Track
+status: raw
+tags: chat
+editor: Jazz Alyxzander<jazz@status.im>
+contributors:
+---
+
+
+
+## Abstract
+
+
+## Background / Rationale / Motivation
+In a multi-protocol environment, it is not always possible for clients to determine how to decode a received message.
+This is especially true when deploying a new version of a protocol, as older clients do not have the logic to decode these new payloads. 
+
+If clients cannot deterministically decode messages then they must attempt decoding the payload into each possible type. 
+In this context failure to decode a message leads to ambiguity as to whether the payload is corrupted or simply an unsupported format.”
+
+Decoding hints can be encoded into the transport medium, however this results in the data being tightly coupled to a specific implementation - which makes versioning more difficult.  
+ Payloads should be self-describing, allowing decoding without depending on details within a specific version of the software.
+
+Having a mechanism to identify which protocol generated a payload, makes decoding more efficient and straightforward. 
+
+
+## Theory / Semantics
+This specification introduces a lightweight tagging scheme for identifying payload types in a multi-protocol environment. It enables clients to determine how to decode payloads without trial-and-error, even when multiple protocol versions exist.
+
+Each payload is tagged with a reference to the specification which defines its structure. 
+Tagging acts as a reference to the protocol specification that defines the payload’s structure.
+As each payload contains a link to the associated specification, clients can decode the message accordingly. 
+
+To accomplish this the wire format includes two different Identifiers. 
+1. domain: the governing body who oversees tag registration.
+2. tag: which specification defines this payload type.
+
+### Tags
+
+Tags are a mapping of a numeric to a specification. Numeric values are used in this context to save space in the payload.
+
+The mapping MUST contain at least the tag value and a link to the associated specification for the payload. It CAN include more data as necessary. 
+How the tags are managed is outside of this specification and is up to the domain.
+
+- Tags MUST NOT be reused.
+- Tags SHOULD correspond to the specifications number if there is one.
+- Tags SHOULD only be used for identifying the root data type. 
+Its assumed that all types from the root can be decoded deterministically. 
+
+### Registries
+registries are a mapping of a numeric to a authority responsible for managing tag values. Numeric values are used in this context to save space in the payload.
+
+
+`registry` mappings can be found in appendix A.
+
+### Decoding
+
+Clients can safely ignore payloads which they do not understand. 
+
+
+## Wire Format Specification
+
+These types are defined using Protobuf V3.
+
+```
+message TaggedPayload {
+	uint32 registry = 1;            // Mapping to specification registry
+	uint32 tag = 10;                // Mapping to type specification
+	bytes payload_bytes = 20;       // Encoded object
+}
+```
+
+## Security/Privacy Considerations
+
+Explicitly tagging payloads with their type does not meaningfully leak metadata. 
+To provide any privacy protections contents need to be encrypted. Occluding the payloads only slows an adversary from decoding that data. 
+
+In cases where the payloads are unencrypted and the type secrecy is critical, payload tagging should not be used.
+
+
+## Copyright
+
+Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).
+
+## References
+
+A list of references.
+
+## Appendix A: Registries
+
+
+
+| Month    | Name | Link                                                 |
+| -------- | -----| ---------------------------------------------------- |
+| 0        | Vac  | https://github.com/vacp2p/rfc-index                  |