Placeholder names are commonly used in cryptography to indicate the participants in a conversation, without resorting to terminology such as "Party A," "eavesdropper," and "malicious attacker."

The most commonly used names are:

• Alice andBob, two parties who want to send messages to each other, occasionally joined byCarol, a third participant
• Eve, a passive attacker who is eavesdropping on Alice and Bob's conversation
• Mallory, an active attacker ("man-in-the-middle") who is able to modify their conversation and replay old messages