    @inproceedings {Roman2005d,
	title = {Protection Against Spam using Pre-Challenges},
	booktitle = {20th IFIP International Information Security Conference (IFIP-SEC{\textquoteright}05)},
	year = {2005},
	month = {May},
	pages = {281-294},
	publisher = {Springer},
	organization = {Springer},
	address = {Chiba (Japan)},
	abstract = {<p>Spam turns out to be an increasingly serious problem to email users. A number of anti-spam schemes have been proposed and deployed, but the problem has yet been well addressed. One of those schemes is challenge-response, in which a challenge is imposed on an email sender. However, such a scheme introduces new problems for the users, e.g., delay of service and denial of service attacks. In this paper, we introduce a pre-challenge scheme that avoids those problems. It assumes each user has a challenge that is defined by the user himself/herself and associated with his/her email address, in such a way that an email sender can simultaneously retrieve a new receiver{\textquoteright}s email address and challenge before sending an email in the first contact. Some new mechanisms are employed to reach a good balance between security against spam and convenience to email users.</p>
},
	isbn = {0-387-25658-X},
	author = {Rodrigo Roman and Jianying Zhou and Javier Lopez},
	editor = {Ry{\^o}ichi Sasaki and Sihan Qing and Eiji Okamoto and Hiroshi Yoshiura}
}
