Dao Ke Dao (道可道) -- Message Module (Python)

This document introduces a common Message Module for decentralized instant messaging.

Features

• Envelope
  • Sender
  • Receiver
  • Time (same value from content.time)
• Content
  • Type
  • Serial Number
  • Time
  • Group (Optional)
• Message
  • Instant Message
  • Secure Message
  • Reliable Message

Envelope

Message Envelope

/* example */
{
    "sender"   : "moki@4WDfe3zZ4T7opFSi3iDAKiuTnUHjxmXekk",
    "receiver" : "hulk@4YeVEN3aUnvC1DNUufCq1bs9zoBSJTzVEj",
    "time"     : 1545405083
}

Content

/* example */
{
    "type"     : "1",       // message type
    "sn"       : 412968873, // serial number (message ID in conversation)
    "time"     : 1545405083,
    
    "text"     : "Hey guy!"
}

Content Type

def i2s(value: int) -> str:
    return '%d' % value


class ContentType:

    ANY = '*'
    # UNKNOWN = i2s(0x00)  # 0000 0000 (Undefined)

    TEXT = i2s(0x01)       # 0000 0001

    FILE = i2s(0x10)       # 0001 0000
    IMAGE = i2s(0x12)      # 0001 0010
    AUDIO = i2s(0x14)      # 0001 0100
    VIDEO = i2s(0x16)      # 0001 0110

    # Web Page
    PAGE = i2s(0x20)       # 0010 0000

    # Name Card
    NAME_CARD = i2s(0x33)  # 0011 0011

    # Quote a message before and reply it with text
    QUOTE = i2s(0x37)      # 0011 0111

    MONEY = i2s(0x40)          # 0100 0000
    TRANSFER = i2s(0x41)       # 0100 0001
    LUCKY_MONEY = i2s(0x42)    # 0100 0010
    CLAIM_PAYMENT = i2s(0x48)  # 0100 1000 (Claim for Payment)
    SPLIT_BILL = i2s(0x49)     # 0100 1001 (Split the Bill)

    COMMAND = i2s(0x88)        # 1000 1000
    HISTORY = i2s(0x89)        # 1000 1001 (Entity History Command)

    # Application Customized
    APPLICATION = i2s(0xA0)       # 1010 0000 (Application 0nly, Reserved)
    # APPLICATION_1 = i2s(0xA1)   # 1010 0001 (Reserved)
    # ...                         # 1010 ???? (Reserved)
    # APPLICATION_15 = i2s(0xAF)  # 1010 1111 (Reserved)

    # CUSTOMIZED_0 = i2s(0xC0)    # 1100 0000 (Reserved)
    # CUSTOMIZED_1 = i2s(0xC1)    # 1100 0001 (Reserved)
    # ...                         # 1100 ???? (Reserved)
    ARRAY = i2s(0xCA)             # 1100 1010 (Content Array)
    # ...                         # 1100 ???? (Reserved)
    CUSTOMIZED = i2s(0xCC)        # 1100 1100 (Customized Content)
    # ...                         # 1100 ???? (Reserved)
    COMBINE_FORWARD = i2s(0xCF)   # 1100 1111 (Combine and Forward)

    # Top-Secret message forward by proxy (MTA)
    FORWARD = i2s(0xFF)           # 1111 1111

Message

When the user want to send out a message, the client needs TWO steps before sending it:

1. Encrypt the Instant Message to Secure Message;
2. Sign the Secure Message to Reliable Message.

Accordingly, when the client received a message, it needs TWO steps to extract the content:

1. Verify the Reliable Message to Secure Message;
2. Decrypt the Secure Message to Instant Message.

    Message Transforming
    ~~~~~~~~~~~~~~~~~~~~

    Instant Message  <-->  Secure Message  <-->  Reliable Message
    +-------------+        +------------+        +--------------+
    |  sender     |        |  sender    |        |  sender      |
    |  receiver   |        |  receiver  |        |  receiver    |
    |  time       |        |  time      |        |  time        |
    |             |        |            |        |              |
    |  content    |        |  data      |        |  data        |
    +-------------+        |  keys      |        |  keys        |
                           +------------+        |  signature   |
                                                 +--------------+
    Algorithm:
        data      = password.encrypt(content)
        key       = receiver.public_key.encrypt(password)
        signature = sender.private_key.sign(data)

Instant Message

/* example */
{
    //-------- head (envelope) --------
    "sender"   : "moki@4WDfe3zZ4T7opFSi3iDAKiuTnUHjxmXekk",
    "receiver" : "hulk@4YeVEN3aUnvC1DNUufCq1bs9zoBSJTzVEj",
    "time"     : 1545405083,
    
    //-------- body (content) ---------
    "content"  : {
        "type"  : "1",       // message type
        "sn"    : 412968873, // serial number (ID)
        "time"  : 1545405083,
        
        "text"  : "Hey guy!"
    }
}

content -> JsON string: {"sn":412968873,"text":"Hey guy!","type":1}

Secure Message

/**
 *  Algorithm:
 *      string = json(content);
 *      PW     = random();
 *      data   = encrpyt(string, PW);      // Symmetric
 *      key    = encrypt(PW, receiver.PK); // Asymmetric
 */
{
    //-------- head (envelope) --------
    "sender"   : "moki@4WDfe3zZ4T7opFSi3iDAKiuTnUHjxmXekk",
    "receiver" : "hulk@4YeVEN3aUnvC1DNUufCq1bs9zoBSJTzVEj",
    "time"     : 1545405083,
    
    //-------- body (content) ---------
    "data"     : "9cjCKG99ULCCxbL2mkc/MgF1saeRqJaCc+S12+HCqmsuF7TWK61EwTQWZSKskUeF",
    "keys"     : {
        "hulk@4YeVEN3aUnvC1DNUufCq1bs9zoBSJTzVEj" : "WH/wAcu+HfpaLq+vRblNnYufkyjTm4FgYyzW3wBDeRtXs1TeDmRxKVu7nQI/sdIALGLXrY+O5mlRfhU8f8TuIBilZUlX/eIUpL4uSDYKVLaRG9pOcrCHKevjUpId9x/8KBEiMIL5LB0Vo7sKrvrqosCnIgNfHbXMKvMzwcqZEU8="
    }
}

Reliable Message

/**
 *  Algorithm:
 *      signature = sign(data, sender.SK);
 */
{
    //-------- head (envelope) --------
    "sender"   : "moki@4WDfe3zZ4T7opFSi3iDAKiuTnUHjxmXekk",
    "receiver" : "hulk@4YeVEN3aUnvC1DNUufCq1bs9zoBSJTzVEj",
    "time"     : 1545405083,
    
    //-------- body (content) ---------
    "data"      : "9cjCKG99ULCCxbL2mkc/MgF1saeRqJaCc+S12+HCqmsuF7TWK61EwTQWZSKskUeF",
    "keys"      : {
        "hulk@4YeVEN3aUnvC1DNUufCq1bs9zoBSJTzVEj" : "WH/wAcu+HfpaLq+vRblNnYufkyjTm4FgYyzW3wBDeRtXs1TeDmRxKVu7nQI/sdIALGLXrY+O5mlRfhU8f8TuIBilZUlX/eIUpL4uSDYKVLaRG9pOcrCHKevjUpId9x/8KBEiMIL5LB0Vo7sKrvrqosCnIgNfHbXMKvMzwcqZEU8="
    },
    "signature" : "Yo+hchWsQlWHtc8iMGS7jpn/i9pOLNq0E3dTNsx80QdBboTLeKoJYAg/lI+kZL+g7oWJYpD4qKemOwzI+9pxdMuZmPycG+0/VM3HVSMcguEOqOH9SElp/fYVnm4aSjAJk2vBpARzMT0aRNp/jTFLawmMDuIlgWhBfXvH7bT7rDI="
}

(All data encode with BASE64 algorithm as default)

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