The increasing popularity and importance of electronic commerce is evident today. However, global electronic commerce will not fully develop its immense potential unless trust is fully established. Digital certificates and electronic signature contribute to increase confidence and security by providing authenticity. However, authenticity on its own is not enough to provide trust. A credible service needs to provide authenticity and validity at the same time. In this sense, traditional Public Key Infrastructure (PKI) services have revealed a weak point due to inherent delays existing in order to cancel the possible use of a certificate when it has been lost or stolen. The CertiVeR Project intends to solve this problem and to strengthen security in commercial transactions. CertiVeR has adopted speaker verification (SV) to validate the usersÂ’ identities. The performance of the SV system has been evaluated with a Spanish database that gathers fixedline and mobile telephone sessions.