The digital signature carried by this component is valid, ensuring that the component has not been replaced or altered since ...

The digital signature carried by this component is valid, ensuring that the component has not been replaced or altered since it was signed.  The accompanying digital certificate is also valid.  Digital certificates contain the name of the issuer of the certificate, the name of the subject of the certificate (i.e., the publisher of the component), the subject's public key, and other information.  The issuer is in turn represented by its own certificate, and so on, recursively.  You can view all the information in the whole certificate chain by clicking the "View Certificate" button below.  %1The choice in the previous dialog to "always trust components signed by this publisher" really means to "always trust components validly signed and accompanied by this certificate," since the certificate declares the publisher's identity.

The publisher digitally signed the component, using its private key corresponding to its public key in the certificate.  By cryptographic theory, the validity of the digital signature of the component (which SharePoint Workspace has verified for you) guarantees that the component has not been modified since the publisher signed it.  The certificate chain and the signature on the component together provide the basis for determining how much trust you can justifiably invest in the authorship of the component, and in the functionality of the component.  If necessary to provide further assurance, you should scrutinize the publisher more carefully - such as by visiting its website, making phone calls to it, checking up on its reputation among your acquaintances, etc..  Note that some component publishers may incorporate subcomponents written by subpublishers, and these considerations apply to the subpublishers as well.  SharePoint Workspace does not currently display information about subcomponents and subpublishers, but the publisher should be able to provide that information.

Keep in mind that any software component you install may contain viruses or may otherwise harm your computer.  It is your decision whether or not to install and run this software.  Microsoft Corporation makes no representations or warranties about any third party software you install or use in connection with software products from Microsoft Corporation.  (Any representations and warranties that Microsoft Corporation makes with respect to its own software are not contained herein, but may be found in the appropriate license agreement.)

If you decide not to proceed with the installation of this component, click No.