The LACChain Mailbox is a secure and private system for the exchange of messages, VCs, and VPs based on the DIDComm Messaging Specification. It is a controlled by a centralized server that allows entities identified by a DID to send and receive messages.

Operation Modes

According to the DIDComm Specification, there are two operation modes for an intermediary.

As a Mediator

In this operation mode, the Mailbox provides a REST API that can be accessed by any application using the DIDConnect Authentication Protocol.

To send a message using the Mailbox as a Mediator, the subject A must encrypt the message to C and then wrap again into an encrypted envelope to B (Mailbox). Once the Mailbox receive the message it will unwrap the envelope and just storage the message encrypted to C.

As a Relay

It is also possible to use the Mailbox as a Relay to route messages through different networks or transport protocols.

In this operation mode the Mailbox will only act as a proxy to relay the message to another Mailbox. The message only needs to be encrypted for the recipient, and the mailbox does not unwrap or modify the message in any way.

Message Envelope

Currently, the Mailbox only support authenticated encryption, thus in order to guarantee the integrity and privacy of the message.

The envelope to wrap for Mailbox Mediator is as follows:

{
    "type": "https://didcomm.org/routing/2.0/forward",
    "to": [MAILBOX_DID],
    "expires_time": EXPIRATION_TIME_MILIS,
    "body":{
        "next": RECEIVER_DID,
        "payloads~attach": [
            MESSAGE_ENCRYPTED
        ]
    }
}

DID Service

To resolve the endpoint of Mailbox in a DID document, every sender / receiver must include a Service for messaging purpose.

"service": [{
        "type": "DIDComm",
        "endpoint": "MAILBOX_DID"
}]

When an instance of Mailbox is deployed, it is necessary to specify a DID associated to the Mailbox, and register a DID Service with the url of API as the endpoint.

"service": [{
        "type": "DIDComm",
        "endpoint": "API_URL"
}]

LACChain Endpoint

The official mailbox from lacchain has the following DID:

MAILBOX_DID: did:lac:main:0x5c3968542ca976bec977270d3fe980dd4742865e

And, it can be resolved in the following DID Registry: 0xCC77A5e709cB473F49c943D9b40B989f986E5F2F

API

1. Send a Message

1. Resolve the DID Document of the recipient
2. Get the DIDComm service endpoint
3. Resolve the DID Document of the DIDComm service endpoint
4. Encrypt the message for the recipient using Authenticated Encryption
5. Encrypt the message for Mailbox wrapping the previous message in the envelope described above and using Authenticated Encryption
6. Generate the id_token using the DIDConnect Protocol
7. Send the request to Mailbox API:

POST /vc
Headers:
Content-Type: 'application/json'
token: id_token
Body:
<<Encrypted Message for Mailbox>>

The possible responses for that request are:

1. 200 - The message was successfully received
2. 500 - Authentication error

2. Receive Messages

1. Generate the id_token using the DIDConnect Protocol
2. Send the request to Mailbox API:

GET /vc
Headers:
Content-Type: 'application/json'
token: id_token

The possible responses for that request are:

1. 200 - An array of messages
2. 500 - Authentication error

Pre requisites

• Node > v14.4
• Redis

Testing

npm install
npm test

Deploy

npm install
npm start