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OPTIMISTIC FAIR EXCHANGE PROTOCOLS

  • US 20020049601A1
  • Filed: 10/28/1998
  • Published: 04/25/2002
  • Est. Priority Date: 10/28/1998
  • Status: Abandoned Application
First Claim
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1. A method for the fair exchange of value items such as certified mail, electronic cash payment and receipt, or contract signatures, between two parties (A, B) in a network of arbitrary latency, according to a given protocol, in which method one party (A) receives the value item (itemB) of an other party (B) only if said other party also receives the value item (itemA) of said one party, and in which method a third party (T) is only involved in the exchange in exceptional situations;

  • providing an exchange protocol using permits each of which binds a representation of a value item such that;

    a receiving party (A or B) can verify that the permit binds the representation of an expected value item but cannot obtain said expected value item from the permit, and the third party (T), when receiving the permit and some additional information, can obtain the bound representation of the value item from the permit for delivery to one of the parties, without further cooperation of the two parties;

    the protocol including steps for;

    first sending a permit from each of the two parties to the other one for verification, and then transmitting a representation of a value item from each party to the respective other party if the verification of a previously received permit was satisfactory for the transmitting party;

    the protocol further providing;

    at least one subprotocol (ABORT;

    A-RESOLVE;

    B-RESOLVE) for recovering from an exceptional situation;

    a subprotocol being invoked by one (A or B) of the two parties for involving the third party (T), and including the transmission of a permit and additional information from said one party to the third party;

    the execution of a subprotocol, without further cooperation from any of the two parties, either completing the exchange procedure so that finally each correctly behaving party received a representation of the value item it expected from the respective other party, or terminating the exchange procedure so that none of the parties received the value item it expected from the respective other party.

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