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server_verification_utils

server_verification_hash(challenge)

This hash function is used by the game client to verify communication with a genuine server during connection initialization.

Parameters:

Name Type Description Default
challenge int

The challenge value sent by the client. Should be no larger than 11,092,110.

 required

Returns:

Name Type Description
int int

The hashed challenge value.
Remarks
  • The client sends an integer value to the server in the INIT_INIT client packet, where it is referred to as the challenge.
  • The server hashes the value and sends the hash back in the INIT_INIT server packet.
  • The client hashes the value and compares it to the hash sent by the server.
  • If the hashes don't match, the client drops the connection.
Warning
  • Oversized challenges may result in negative hash values, which cannot be represented properly in the EO protocol.
See Also
Source code in src/eolib/encrypt/server_verification_utils.py 
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def server_verification_hash(challenge: int) -> int:
    """
    This hash function is used by the game client to verify communication with a genuine server
    during connection initialization.

    Args:
        challenge (int): The challenge value sent by the client.
                         Should be no larger than 11,092,110.

    Returns:
        int: The hashed challenge value.

    Remarks:
        - The client sends an integer value to the server in the `INIT_INIT` client packet, where it
          is referred to as the `challenge`.
        - The server hashes the value and sends the hash back in the `INIT_INIT` server packet.
        - The client hashes the value and compares it to the hash sent by the server.
        - If the hashes don't match, the client drops the connection.

    Warning:
        - Oversized challenges may result in negative hash values, which cannot be represented
          properly in the EO protocol.

    See Also:
        - [`InitInitClientPacket.challenge`][eolib.protocol._generated.net.client.InitInitClientPacket.challenge]
        - [`InitInitServerPacket.ReplyCodeDataOk.challenge_response`][eolib.protocol._generated.net.server.InitInitServerPacket.ReplyCodeDataOk.challenge_response]
    """
    challenge += 1
    return (
        110905
        + (_mod(challenge, 9) + 1) * _mod(11092004 - challenge, ((challenge % 11) + 1) * 119) * 119
        + _mod(challenge, 2004)
    )