Can spammers fake stamps by attaching fake signatures to emails?
No. Email signatures are generated by a hash of an email digest and the user’s secret key. A fake stamp cannot be generated without such a key, as issued by the CentMail server. • If only a few people are using CentMail, why should I start using it? Is there a chicken-and-egg problem? To become an effective spam deterrent, many people need to use CentMail. However, regardless of how many other people are using CentMail, each participant gets the immediate benefit of having their causes promoted and perhaps their donations matched. In terms of spam deterrence with partial adoption, CentMail’s guarantee — that the sender paid at least one cent per recipient — is diluted but still meaningful. • Are there hidden costs to using CentMail? Again, the vast majority of users who already make charitable contributions incur no additional monetary expense. Furthermore, there is also no significant computational expense (e.g., spent CPU cycles) or significant human expense (e.g., time spent solvi
