DISA requires a renewal of the software maintenance of their Tumbleweed repeater and Tumbleweed responder software currently in use as part of the Robust Certificate Validation System (RCVS) portion of the PKI architecture.  This order is in support of the Public Key Infrastructure (PKI) program.  PKI is a service of products that provide and manage X.509 certificates for public key cryptography.  Certificates identify the individual named in the certificate, and bind that personto a particular public/private key pair.  The RCVS provides responses to user's requests to the validity status of certificates via the Online Certificate Status Protocol (OCSP) so that personnel may log into websites, PCs, etc.  This service is provided directly to various DoD networks or to the Services for redistribution throughout their domains.  This software is part of a suite of products used to insure the maximum interoperability with clients deployed throughout DoD.