| Internet-Draft | SIME | September 2025 |
| Dutta | Expires 20 March 2026 | [Page] |
This document specifies the SIME protocol, a decentralized, atomic protocol for inter-domain mail transmission and entity-to-entity communication. It defines packet types, headers, MX/SRV-based trust verification, TCP-based delivery, and SIME Extensions for attachments. All servers act as Domain Authorities (DA), and inter-domain transactions are governed by atomic protocol rules.¶
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SIME (Srijal's Integrated Mail Extensions) is a decentralized protocol designed to provide reliable messaging between users in different Domain Authorities (DA). Each DA manages its own user authentication and registration rules. Atomic protocol enforcement ensures inter-domain transactions follow strict compatibility, reliability, and security rules.¶
All SIME traffic is conducted over TCP to ensure reliable delivery.¶
DA (Domain Authority) - Server managing a domain and its users¶
ID - Disposable session identifier (e.g., JWT)¶
Transaction ID - Identifier assigned per transaction session¶
TCP - Transmission Control Protocol (mandatory transport)¶
MAIL Packet - Packet containing mail messages¶
CONV Packet - Packet for general communication¶
MX/SRV Record - DNS record or SRV record pointing to server endpoint for inter-domain verification¶
- Users authenticate with their DA and receive disposable IDs.¶
- Communication is TCP-only to prevent packet loss.¶
- Two primary packet types: CONV and MAIL.¶
- Inter-domain transactions require MX/SRV verification to ensure messages reach the correct DA server.¶
- Atomic rules enforce uniformity; non-compliant servers are rejected.¶
CONV Packets:¶
Used for login and general communications:¶
LOGIN <username> <password> START TRANSACTION <ID> CONV <payload>
MAIL Packets:¶
Used for sending messages:¶
PREPARE HEADERS <transact_id> X-Mailed-Type-Render: <TXT|MD|HTML>; RECIPIENT: user@domain PREPARE MESSAGE <transact_id> <content> END TRANSACTION <transact_id>
- SENDER: Originating user (user@domain)¶
- RECIPIENT: Destination user (user@domain)¶
- X-Mailed-Type-Render: TXT | MD | HTML¶
- Optional headers may be added via SIME Extensions¶
Users initiate login via CONV packet:¶
LOGIN <username> <password>
Server responses:¶
SUCCESS LOGIN : <ID> ERROR AUTH
Disposable IDs are required for subsequent packets.¶
1. User logs in: CONV Packet → LOGIN → SUCCESS LOGIN : <ID>¶
2. User initiates transaction: CONV Packet → START TRANSACTION <ID>¶
3. Server validates ID:¶
- Success → returns transaction acknowledgment¶
- Failure → returns ERROR AUTH¶
4. User sends MAIL packet:¶
- PREPARE HEADERS <transact_id> ...¶
- PREPARE MESSAGE <transact_id> <content>¶
5. User ends transaction: END TRANSACTION <transact_id>¶
6. Server responds with SENT or appropriate error.¶
- No version negotiation; all inter-domain servers must implement the exact protocol.¶
- Non-compliant servers are rejected.¶
- Transactions must be atomic: either all steps succeed or fail.¶
- DA MX/SRV record must point to verified server endpoint.¶
- Messages are sent only to verified MX/SRV endpoints.¶
- Servers not listed or failing verification are rejected.¶
- ERROR AUTH : Invalid login/session¶
- ERROR TRANS : Transaction initiation failure¶
- ERROR HEADER : Invalid or missing headers¶
- ERROR MXVER : Inter-domain MX/SRV verification failure¶
- ERROR PACKET : Malformed packet¶
- ERROR SEND : Message could not be delivered¶
- All packets use TCP for reliable delivery.¶
- Authentication handled per DA; disposable IDs required.¶
- TLS is recommended for inter-domain traffic.¶
- Disposable IDs and transaction IDs mitigate replay attacks.¶
- Inter-domain trust relies on MX/SRV verification; unverified endpoints are rejected.¶
- Confidentiality and integrity of message content require TLS or optional message signing.¶
- Reviewers should note that deployment must account for standard-compliant DNS/SRV usage instead of arbitrary IP:PORT MX records.¶
- Each DA must publish a SIME MX or SRV record specifying its server endpoint.¶
- Inter-domain messages are routed only to verified endpoints.¶
- Unverified endpoints are rejected.¶
- ATTACHMENT: <filename>¶
- ENCODING: base64 | hex¶
- Optional metadata headers supported¶
- Attached in content as: <UNICODE UTF-8: 0xEF 0xBF 0xBF><hex|base64> <encoded attachment><UNICODE UTF-8: 0xEF 0xBF 0xBF>¶
CONV-PACKET = LOGIN-PACKET / TRANSACTION-PACKET / GENERAL-CONV
LOGIN-PACKET = "LOGIN" SP USERNAME SP PASSWORD CRLF
TRANSACTION-PACKET = "START TRANSACTION" SP ID CRLF / CONV SP PAYLOAD CRLF
MAIL-PACKET = "PREPARE HEADERS" SP TRANSACTION-ID SP HEADER-FIELDS CRLF
"PREPARE MESSAGE" SP TRANSACTION-ID SP CONTENT CRLF
"END TRANSACTION" SP TRANSACTION-ID CRLF
USERNAME = 1*(ALPHA / DIGIT / "-" / "_")
PASSWORD = 1*(ALPHA / DIGIT / SYMBOL)
TRANSACTION-ID = 1*DIGIT
HEADER-FIELDS = *(HEADER-NAME ":" SP HEADER-VALUE CRLF)
CONTENT = *(OCTET)
User DA-A DA-B | LOGIN | | |------------------>| SUCCESS LOGIN | | START TRANSACTION | | |------------------>| TRANS_ID: 67890 | | PREPARE HEADERS | | |------------------>| PROCEED | | PREPARE MESSAGE | | |------------------>| PROCEED | | END TRANSACTION | | |------------------>| SENT |
Srijal Dutta¶
Email: srijaldutta.official+sime@gmail.com¶