<Li> Encryption and / or sender authentication of e-mail messages (e.g., using OpenPGP or S / MIME) </Li> <Li> Encryption and / or authentication of documents (e.g., the XML Signature or XML Encryption standards if documents are encoded as XML) </Li> <Li> Authentication of users to applications (e.g., smart card logon, client authentication with SSL). There's experimental usage for digitally signed HTTP authentication in the Enigform and mod_openpgp projects </Li> <Li> Bootstrapping secure communication protocols, such as Internet key exchange (IKE) and SSL . In both of these, initial set - up of a secure channel (a "security association") uses asymmetric key--i.e., public key--methods, whereas actual communication uses faster symmetric key--i.e., secret key--methods . </Li>

How does public key infrastructure (pki) work