I have a user A and a user B. They do not trust each other. So, they run the following smart contract:

  1. User A specify a time locked deposit of x coins to user B under a predefined condition( For example: revealing the correct solution of a function ∅(i))

  2. If the user B within a specific time T sends a valid solution, so User B gets the deposit.

  3. Otherwise, if the user B does not sent any correct solution or misbehave by sending non valid solution. Then, User B get fined with x coins that goes to user A.

1 Answer 1


Your scenario is basically a mixed up version of classic and multisig escrow contract.

Multisignature (multisig) refers to requiring more than one key to authorize a transaction. It is generally used to divide up responsibility for possession.

If User B solved the ∅(i) in stipulated time T then contract releases the escrow, This one is classic example of contract. The only thing that is new as from your last line is that if user B behaves wrongly then some fine will be levied from him. To achieve this both A and B have to deposit some amount of mutual agreed coins to smart contract.

1. User A

2. user B

3. Mutual agreed smart contract rules

A fair implementation of Multisig Smart Contract:



  • Why we need the Mutual agreed neutral person. The blockchain mainly removes the need for the trusted third parties. This paper allow fair execution with bitcoin link.springer.com/chapter/10.1007/978-3-662-44381-1_24 But I am not sure why in your answer specified a third party. I need only 2 parties to agree on the conditions I mentioned in my question. Commented Feb 6, 2019 at 5:38
  • with 2 parties there is always fair chance of conflict, See the ETHlend smart contract which is P2p Lending platform : etherscan.io/address/… Commented Feb 6, 2019 at 5:46
  • @HebaMohsen, i edited my answer : by 3rd person i meant the mutual agreed smart contract rules not person. Commented Feb 6, 2019 at 5:48
  • Do you mean: in bitcoin , 2 users can agree on a transaction, that can be redeemed upon a greed condition. Do you have any idea how that happen on etherum??
    – Mohamed
    Commented Feb 6, 2019 at 6:39

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