1. open PGPkeys.

2. Right-click the public key item and select Export.

3. In the Export Key to File dialog box, keep the default file name and save it to the teacher's computer. The path is \Teacher\share and the file name is studentx(x is the seat number).

4. open Microsoft Outlook Express (start > programs > Outlook Express).

5. Configure Outlook Express as follows: account name -SX (X is the seat number), email address-sx@linux-online.com, POP3/SM. TP server address-192.168.0.14 (the actual situation may be different).

6. Send the public key file to the partner, or get the partner's public key file from the path \Teacher\share.

7. Open the Keys menu in PGPkeys and select Import.

8. In the Select Include File dialog box, locate and select the partner's public key file, and then click the Open button.

9. In the Select Key dialog box, select the public key file to import, and then select Import.

10. Right-click the imported public key and select Signature.

1 1. Highlight the public key and select the Allow signature export check box.

12. When asked for a password, please enter your own private key.

13. Right-click the partner's public key and select Key Properties.

14. At the bottom of the dialog box that appears, drag the slider indicating trust status from untrusted to trusted.

If you don't do the above steps, when you receive an encrypted signature email from the other party, you will find an invalid prompt next to the signature status after unlocking, indicating that you don't fully trust this key.