In this illustration, we see Alice looking rightwards. Above her is a message, m, and below her is a message, m. A blue arrow extends from the top message to a white box labeled H(.) and extends through the box to a second box, this one-labeled K (-/A) (.). The arrow, now labeled KA- (H(m)), continues rightward then vertically downward to a circle labeled "+."

A blue arrow extends from the bottom message horizontally rightward, then vertically upward to the circle labeled "+."A blue arrow points rightward from the circle to a cloud representing the Internet. This entire process is labeled "Alice sends e-mail message m."

A blue arrow extends rightward from the Internet to a circle labeled "-." A blue arrow extends vertically upwards from the circle, then horizontally rightward, now labeled KA- (H(m)), to a box labeled KA+ (.). The arrow extends rightward, then vertically downward to a blue diamond labeled "Compare."

A blue arrow containing the message also extends from the circle vertically downward and then horizontally rightward to a white box labeled H(.). The arrow continues rightward and then vertically upwards to the diamond labeled "Compare." This entire process is labeled "Bob receives e-mail message m."