The rise of e-marketplaces on the Internet is going to bring a broad new set of business opportunities to enterprises and customers at a fraction of the physical-world costs. However, to be really successful, these e-marketplaces must be open, trusted, fair and transparent. They must be able to convey on-line the same feeling of trust, security and privacy that traditional marketplaces do. This has implication on three critical aspects: the decisions to be made about membership of traders; their admissibility to negotiations; the controls over the negotiation processes. In this paper we discuss a novel method for automating the admittance to negotiation within marketplaces consistently with traders' privacy requirements. 10 Pages