[ Thanks to linuxaria for this link.
“In the previous article we presented some basic
concepts of encryption and made some examples of symmetrical and
asymmetrical keys, we concluded by saying that a good way to get a
certificate with an asymmetric key is GnuPG.
“GnuPG is open-source and multiplatform. It uses native command
line in a shell or from MS-DOS prompt.
“There are also graphical interface:
“Enigmail it’s an extension for Mozilla thunderbird. And
contains a graphical tool for keys management.”