However, a successful cryptographer must be cautious at a level that would be judged paranoid in more civilized communities. A correct analysis of the risks and the costs of prevention and non-prevention is not being paranoid. To be overly cautious is, almost by definition, not to be economical. It should be noted, however, that there is enormous risk in ignorance of the other risks, and so effort made in order to understand the risks is well spent, _even_ if one spends more on that than the savings stemming from that understanding. If you need cryptography, it's because you have enemies. This is dangerously false. One uses crypto because one does not know the nature of one's opponents now and in the future, with an emphasis on the future. This lack of knowledge includes an ignorance that certain parties do not have your best interests at heart. If you think they do, you can always reveal the information. Cryptography is primarily about how we get assurances of security. Uncertainty has negative value all by itself. Eric