Figure 8

The process of information exchange between the selling and the buying robots comprises four steps. Step 1: A selling robot makes an offer to a buying robot. This offer includes the target (food or nest), information age, and a maximum block number which specifies when the light contract must be included in the blockchain at the latest. Step 2: If a buying robot agrees on the offer, it returns its signature of the offer and its corresponding public key. In addition, it returns its relative position to the selling robot. Both parties now possess a double-signed light contract. The light contract is an off-chain agreement between two robots that is fast to perform since it does not require a transaction on the blockchain network. Step 3: The selling robot creates a blockchain transaction that includes both the light contract and the now revealed path information to the target site in the buyer’s reference frame. Step 4: The smart contract performs three security checks before it adds the transaction to the blockchain. These checks ensure that the terms of the light contract were not violated. If one of the checks fails, the transaction is discarded.