MIP - Programmable Envelopes

[robdefeo]

Simple Summary

Allow creating transaction data in a more flexible and clear way. Using functions/structs linked to an ID to describe each payload type and its contents.

Abstract

To address different message requirements and payload handling options, this proposes introduction of a programmable envelope to 'enclose' a message. The envelope type defines the payload options.

This achieves a flexible and efficient means of sending message payload without introducing unnecessary complexity through many optional fields that would require complex documentation and a lousy developer experience.

Without this, forward and backward compatibility is possible but requires complex test cases and carries greater risks of fields conflicting.

Motivation (*optional)

Different types of messages SHOULD be supported on Mailchain, including but not limited to:

• Private location, privately verifiable message contents
• Private location, public verifiable message contents
• Using full URL for message location
• Using full Message Storage Identifier (see MIP - Message Store Identifier #215 ) for message location
• Public (unencrypted) message, stored in txdata
• Public (unencrypted) message location with public unencrypted message

Specification

• ID to link to different envelope being used.
• ID = 0x00 is reserved to identify unset value
• ID = 0xFF and above is reserved to allow extensibility beyond 256 envelopes using the next byte to identify length.
• Data should be able to validate if its contents are invalid Valid() error
• Return URL encrypted or not URL(decrypter cipher.Decrypter) (*url.URL, error)
• Return hash to ensure data has not been altered IntegrityHash(decrypter cipher.Decrypter) ([]byte, error)
• Return hash to ensure contents has not been tampered ContentsHash(decrypter cipher.Decrypter) ([]byte, error)

Rationale

See abstract

Backwards Compatibility

This will allow backwards and forwards compatibility as long as the first byte identifies its envelope type and the interface is implemented

Related MIP

• MIP - Alpha envelope MIP - Alpha envelope #218
• MIP - Message Location Identifier Envelope MIP - Message Location Identifier Envelope #219

[tboeckmann]

I edited the abstract... this is a great proposal.

Where are the IDs stored?

[robdefeo]

Currently the ID's are stored in https://github.com/mailchain/mailchain/blob/master/internal/envelope/data.go now you mention it. I didn't give it much thought when creating it like this though. Any requirements you can think of around that?

[tboeckmann]

Currently the ID's are stored in https://github.com/mailchain/mailchain/blob/master/internal/envelope/data.go now you mention it. I didn't give it much thought when creating it like this though. Any requirements you can think of around that?

I think a CSV in the repo is fine for now. Developers can create a pull request to suggest entries. Each envelope should have sufficient accompanying documentation.