1. A computer implemented method for validating SCEP certificate enrollment requests, said method comprising the steps of, in combination: allowing trusted users to register SCEP challenges and associated sets of expected certificate content for the SCEP challenges; electronically receiving a certificate request from via a communications network; electronically validating the certificate request by checking whether a SCEP challenge of the certificate request matches one of the previously registered SCEP challenges and if so checking whether content of the certificate request matches the previously registered expected certificate content associated with the matching registered SCEP challenge; authorizing a certificate if the SCEP challenge of the certificate request matches a previously registered SCEP challenge and the content of the certificate request matches the registered expected certificate content associated with the matching registered SCEP challenge; and denying the certificate if the SCEP challenge of the certificate request does not match a previously registered SCEP challenge or if the content of the certificate request does not match the registered expected certificate content associated with the matching registered SCEP challenge.