Requirement of the recipient on disputes

The requirement of the recipient on disputes Once a recipient has accepted a certain message as authenticated by a certain signer (in an authentication transaction), he should win disputes about that message in court. The only exception is with schemes like invisible signature schemes, where disputes only work if the signer cooperates. 

State Correct init use needed Figure 5.8. Sketch of the requirement of the recipient on disputes... 

One can easily obtain a formal version of this strong requirement of the recipient on disputes from the weak one by replacing the predicate recipient weakly wins by the predicate... 

These security types are mainly treated in Section 5.4.3. With the ordinary type of security, known from ordinary digital signature schemes, the requirement of the recipient on disputes is guaranteed with the high degree of security, whereas the court may wrongly decide for the recipient in extreme situations. To its right, a type of security dual to ordinary security is shown. 

This definition and the requirement of the recipient on disputes imply what the second recipient in a transfer would require from disputes, because there is no formal difference between accepting a message as authenticated in authentication and in a transfer. ... 

The requirement of the recipient on disputes is extended to recipients in transfers (with i < X). If one has required unforgeability, it is extended so that nobody accepts a message as authenticated with any acceptance level as long as a signer has not authenticated it. 

If the requirement of the signer on disputes (or the fall-back requirement) is fulfilled without error probability, the requirement of the recipient on disputes (or the correctness of broken ) is not fulfilled at all. 

For Statement 3, assume that the requirement of the recipient on disputes is error-free. Thus, whenever an execution of authentication with the recipient s entity leads to acc = TRUE, the recipient will win a subsequent dispute in court. A computationally unrestricted attacker comprising the recipient s entity can search for a sequence of messages that would lead to acc = TRUE if the correct recipient s entity received them in authentication. Then this attacker can win disputes deterministically. Hence the requirement of the signer can only be fulfilled against computationally restricted attackers in this case. 

The fail-back requirement of the recipient on disputes is that once the recipient has accepted a message m as authenticated by a signer, a court in a dispute about this message should obtain a result acc TRUE, broken . ... 

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