Bob is now in possession of Alice's padlocks, but not the unlocking codes. When Bob wants to send Alice a confidential letter, he places the letter inside a steel box and locks it with one of Alice's padlocks. Once the padlock is snapped shut, even he himself cannot re-open the box since he is not in possession of the combination which will release the lock. Only Alice will be able to open the box and therefore read the letter once she has received Bob's parcel in the mail. Public key encryption works much in the same manner. The public key may be thought of as an open, electronic padlock. You can send this electronic padlock to all your friends. Your friends may then use that padlock to secure their emails to you in an electronic box. This electronic box is the encrypted email. Upon receipt of the encrypted email, you dial the secret combination which is your private key and retrieve the original message. SecExMail does all this for you. |
