HW17: Ponzi-scheme

Problem statement

Implement a smart contract for a Ponzi-scheme.

• The contract represents an organization.
• The creator of the contract is the first member of the organization.
• Any new members must refer to exactly one already existing member.
• New members have to pay at least 10 ether when joining.
• This joining fee is distributed equally along the referral chain, but at most on three levels. (See the example below for clarification.)

Example scenario

Alice decides that she wants to create an organization based on the Ponzi-scheme (which is illegal).

When Bob joins, he sends 10 ether and refers Alice. Thus, Alice gets 10 ether.

When Clair joins, she sends 10 ether and refers Bob. Thus, Bob, and Alice both get 5-5 ether (as Bob referred Alice).

When Dan joins, he sends 15 ether and refers Claire. Thus, Claire, Bob, and Alice all get 5-5 ether.

When Eve joins, she sends 15 ether and refers Dan. Thus, Dan, Claire and Bob all get 5-5 ether. But this time Alice does not get anything, i.e. we go "up" the referral chain for at most 3 levels.

Contract interface

• constructor: function Ponzi()

  • Creates an organization with the sender of the transaction (msg.sender) being the first member.

• join: function join(address inviter) payable

  • The sender of the transaction joins the organization, referring inviter.
  • Succeeds only if inviter is a member, but the sender of the transaction is not.
  • The sender must send at least 10 ether to be able to join.
  • The funds sent along are distributed equally between inviter, the member referred by inviter, and the member referred by the member referred by inviter (see the example above for clarification).

Contract skeleton

pragma solidity ^0.4.21;

contract Ponzi {

    // <contract_variables>

    // </contract_variables>

    function Ponzi() public {
        // TODO
    }

    function join(address inviter) public payable {
        // TODO
    }

}