User authentication and validation for performing transactions may be performed by a validation server of a service provider. For example, when a login request or purchase request is received, the request may be authenticated or validated before permitting the requested transaction. In some arrangements, the validation may be delegated to one or more devices or users external to the service provider. Multiple validation users may be consulted for each transaction request to determine a consensus validation decision. A consensus may be reached based on unanimous responses or based on a specified threshold level (e.g., more than 50% responding positively or negatively). The service provider may use this consensus determination to authorize or reject a transaction request.