A method for aiding transactions by providing warranties against various aspects of a transaction which may be hard to assure ahead of time or when high risk is involved in relying on them. The method employs an infrastructure of a computer and communication systems communication with various distributed organizations working together and providing warranties. Different parties may trust different organizations and user representatives of the infrastructure. A party in a transaction may ask for a warranty against another party. As a response, the infrastructure, through its organizations, calculates and provides a decision regarding the request. Relying on the warranty, the risk involved in conducting the electronic transaction is reduced. In the case where the transaction does not reach sound completion, the warranty can be claimed. The method also involves managing and administering the infrastructure, the entities in the transaction system and their outstanding warranties. Cryptographic sub-systems within the infrastructure components and the entities they serve are used to assure party/organization authentication and the validity of electronically signed messages within the transaction system. The warranty granting process, in turn, assures the transaction: its content, context, the parties and the parties' identification mechanisms, such as digital certificates.