Abstract de la publi numéro 12000

The growing number of Public Key Infrastructure (PKI) and the increasing number of situations where partners of a transaction may carry certificates signed by different certification authority (CA) points out the problematic of trust between the different CAs. Several trust models, like the hierarchy model, cross-certification model, and bridge CA model were proposed in order to establish and extend the domain of trust of relying parties (RP). However, each model has disadvantages and especially the scalability in large open networks like Internet. In this paper, we provide users with quantitative information of the confidence a relying party can have about a certificate. We call this information quality of certificate (QoCER). QoCER depends on two parameters which are the quality of procedures announced in the certificate policy (CP) and the quality of CA (QoCA) that represents the evaluation of the CA commitment to its policy. QoCA is calculated based on the recommendation of different actors (audit agency, RP, etc.). QoCER is balanced by another information that represents the confidence on QoCA calculation. We present a formal model of trust to calculate these values.