dMsg_system_overview.md

dMsg (ICPanda Message) System Overview

dMsg On-Chain Side

Backend Smart Contracts

• Management canister:
  • Source code: ic_message
  • Description: The management canister that handles users management, canisters management, price management and channels management.
  • ic_message canister: nscli-qiaaa-aaaaj-qa4pa-cai
• User public profile canister:
  • Source code: ic_message_profile
  • Description: The profile canister that handles user public profiles management. The number of profile canisters can be increased based on user scale.
  • ic_message_profile Canister: ijyxz-wyaaa-aaaaj-qa4qa-cai
• Channel canister:
  • Source code: ic_message_channel
  • Description: The channel canister that handles channels management and messages management. The number of channel canisters can be increased based on user scale.
  • ic_message_channel canister: nvdn4-5qaaa-aaaaj-qa4pq-cai
  • ic_message_channel_02 canister: zof5a-5yaaa-aaaai-acr2q-cai
  • ic_message_channel_03 canister: 4jxyd-pqaaa-aaaah-qdqtq-cai
• COSE canister:
  • Source code: ic-cose
  • Description: IC-COSE is a decentralized COnfiguration service with Signing and Encryption on the Internet Computer. Users who register a username gain a dedicated namespace on the COSE service for key derivation, key storage, and other confidential information. The number of COSE canisters can be increased based on user scale.
  • ic_cose_canister canister: n3bau-gaaaa-aaaaj-qa4oq-cai
• OSS canister:
  • Source code: ic-oss
  • Description: IC-OSS is a decentralized Object Storage Service on the Internet Computer. Channels have a dedicated folder on the OSS service to store files. The number of IC-OSS bucket canisters can be increased based on user scale.
  • ic_oss_cluster canister: 5szpn-tiaaa-aaaaj-qncoq-cai
  • ic_oss_bucket canister: 532er-faaaa-aaaaj-qncpa-cai
  • ic_oss_bucket_02 canister: sb6zj-3aaaa-aaaaj-qndla-cai

Channels Management and Access Control

• No public channels.
• After creating a channel, multiple managers and regular members can be invited.
• Managers can remove regular members but cannot remove other managers.
• Users can read channel info and all (encrypted) messages only after joining.
• After joining, users use ECDH to obtain the KEK from managers for encrypting and decrypting the DEK.
• Users encrypt and decrypt messages and files with the DEK on the client side.
• The channel and its data are deleted when the last manager leaves.
• Sending messages and uploading files consume Gas.

dMsg Client Side

Master Key Derivation

The client supports three types of master keys:

• Free users: The master key (I) is generated using an on-chain derived IV and the user’s password. MK = HKDF-SHA-256(argon2id(password, ID), IV)
• Paid users: The master key (II) is generated using an on-chain derived PK and the user’s password. MK = HKDF-SHA-256(argon2id(password, ID), PK)
• Paid users (with vetkey): Once the vetkey feature is live, the master key (III) will be generated using an on-chain derived vetkey and an optional user password. MK = HKDF-SHA-256(argon2id(password, ID), Vetkey)

Key Encryption Key (KEK) Exchanging

• The MK encrypts and decrypts the KEK.
• The KEK is used to encrypt and decrypt the DEK for message channels, with a 1:1 mapping.
• The encryption scheme follows AES-256-GCM as defined in RFC 9053 (COSE).
• The exchanging scheme follows ECDH-ES + X25519 as defined in RFC 9053 (COSE).