The key algorithms that the program uses are also open source and are called “GNU Privacy Guard,” the open-source alternative to patented key cryptography.
Gpg4win will create both keys according to the parameters you specify. It is necessary to know the addressee’s public key in order for the program to work.
It works like this: the information is encrypted with the public key of the receiver, and when he/she receives the document, it is unencrypted using the private key.
The program installs a plugin for the email client MS Outlook with which you are able to encrypt messages from the program interface.