Two companies have been tapped by the Defense Department Public Key Infrastructure Program Management Office to provide digital certificate validation products to users worldwide, the two companies said today.

Tumbleweed Communications Corp. of Redwood City, Calif., and CoreStreet Ltd. of Cambridge, Mass., were both selected by the PKI program office to provide digital certificate validation solutions. Terms of the contracts were not revealed by either company and the Defense Department did not respond to an inquiry.

Tumbleweed’s Valicert Validation Authority was one of the two solutions selected. With common access cards issued to nearly 3.5 million users, the DOD’s Public Key Infrastructure deployment is largest worldwide, Tumbleweed officials said.

Based on the open standard Online Certificate Status Protocol, Tumbleweed’s Validation Authority allows applications to validate the status of a digital certificate in real time, ensuring that revoked credentials cannot be used for secure email, smart card login, Web access or other electronic transactions.

To address validation response time issues, CoreStreet introduced a new architecture called Distributed Online Certificate Status Protocol that cuts validation time to 65 milliseconds, CoreStreet officials said. The system requires file downloads no larger than a few hundred bytes.