Y may wish to consult a famous physician although they have never met. It is unlikely that this can be satisfactorily achieved without a visit to the physician's consulting rooms, perhaps after some introduction. It is possible that the physician's presence in the telephone directory and medical register are part of an elaborate fraud, including bogus consulting rooms, but in practical terms this is unlikely. If during a visit Y obtains his public key from him personally, and hands him his own, then each can thereafter be sure that future dealings are between the same two individuals. 14 Perhaps more plausible cases of previously unknown parties needing assurance of one anothers' identities can arise where a seller claims to be the owner of property whose title is registered.
Examples are registered titles to land or corporate securities.
It is surprising that in the UK at least, neither the Land Registry nor a corporation in which a person holds stock will necessarily have any prior knowledge of his signature, despite the fact that it is his signature on a form of transfer that is necessary to transfer his title to a buyer. This suggests that remarkably low levels of authentication are quite sufficient to enable substantial transactions to proceed on a large scale without significant practical risk. Nevertheless there might come to be significant benefit from attaching a public key to a land or corporate stock title at the time of acquisition, so that the buyer could later use the corresponding private key to authenticate a subsequent dealing. The following account is summarised from a report appearing on 15th April 1997 in The Daily Telegraph , a UK quality newspaper. 18 In 1964 Alan Reeve, then aged 15, murdered a friend of the same age.