Real world applications of public key cryptography

Public key cryptography is used in a wide variety of protocols and data formats, which are implemented by a huge range of application and system software:

• SSL (https) protocol
• SSH (secure remote login, tunneling, etc)
• Digitally signed PDF files (including attachments within the PDF)
• Signed Applets and jar archive files for Java
• Digital signatures in the packaging infrastructure for Debian, Ubuntu and Red Hat Linux distributions, etc.
• PGP/GPG for signed and/or encrypted files and email .
• S/MIME for signed and/or encrypted email
• DNSSEC for securing the DNS
• Internet Key Exchange (IKE) in IPsec for secure low-level TCP/UDP networking
• RFC 3161 for authenticated timestamps
• A variety of other uses, like digital cash and secure transparent voting .