Funds.sol is a smart contract that aims to present some features of the Solidity language in the context of a university exercise. The current implementation is partial and does not fully reflect the requirements defined below, but it is enough to reach the learning objectives.

A group of friends wants to deposit funds in a safe place and guarantee that the funds cannot be withdrawn until at least 2 of the friends authorise the transaction. When at least 2 of the friends have signed a designated contract, the funds can be withdrawn by any of the friends.

How can we solve this problem using traditional techniques?

1. Open Remix IDE;
2. Create a new file Funds.sol and paste into it the script contained in this repository;
3. Compile Funds.sol;
4. Deploy Funds.sol;
5. Deposit funds (for example, 1 Ether) into the smart contract by invoking the fallback function;
6. Try to withdraw (withdrawFunds ()) the smart contract funds. It will not be possible since nobody signed the contract;
7. Sign (writeSignature()) the contract at least 2 times using distinct addresses and by providing names;
8. Withdraw (withdrawFunds()) the funds from the smart contract using one of the addresses used for signatures;

Now try using the Ropsten public test network (team up with someone else)!

9. Install Metamask and follow the wizard;
10. Connect to the Ropsten network;
11. Withdraw funds for free from the Ropsten faucet;
12. As a Remix IDE environment select Injected Web3, so as to interact with Ropsten;
13. (Only one of you) deploy Funds.sol;
14. (The other person) invoke (at address) Funds.sol from the other instance of Remix IDE using the smart contract address;
15. Deposit funds (for example, 1 Ether) into the smart contract by invoking the fallback function;
16. Sign (writeSignature()) the contract at least 2 times using distinct addresses and by providing names;
17. Withdraw (withdrawFunds()) the funds from the smart contract using one of the addresses used for signatures;

Note that in this case the signatures and the names will be written permanently on the Ropsten public test network. Students may use also Etherscan to interact with the the smart contract.

18. Modify the code to require sending a positive amount of Ether to the contract to sign it (replace line 24 of the code with the code below);

 function writeSignature(string memory _name) public payable isOwner(false, "An address can be used only once to sign the contract.") {
  require(msg.value > 0, "A positive amount of Ether is required to sing the contract.");

19. Repeat the process from step 3, taking into consideration the new rule;