Due to each of these methodologies requiring smart contracts to operate on both the origin and destination chain, there needs to be some system connecting the two. Most bridges opt for a centralized approach, since it is the easiest to implement and guarantees control over the transactions taking place. There are, however, ways of achieving this functionality in a decentralized manner, and those do opt for these are called trustless bridges. These usually involve validating transactions in the same way a blockchain does - through miners or validators.