From a security viewpoint, bridges can be classified into two main groups: trusted (also known as custodial) and trustless (noncustodial). Trusted platforms are essentially platforms that rely on third parties to validate transactions while acting as custodians of the bridged assets. For example, all wrapped bitcoin is held in custody by BitGo. Having one company control all of an asset means it is a single point of failure. If the company is corrupt, goes bankrupt or has other fundamental problems, the crypto that it has in custody is at risk.
