What is the classical cryptographic model, and who are Alice, Bob, and Eve?

The classical model has Alice (sender) and Bob (receiver) communicating over an insecure channel, with Eve (attacker) eavesdropping on the channel.

In this model:

• Alice = sender of the message
• Bob = receiver of the message
• Eve = eavesdropper / attacker (from "eavesdropper")
• The communication channel (network) is the attack surface

Key assumptions of the classical model:

• Attacks happen on the communication channel (between Alice and Bob)
• Cryptographic operations occur inside a tamper-proof "black box" (e.g., a hardware security module or smart card)
• Security relies primarily on the mathematical strength of the algorithm and the key size

This model is a simplification. In reality, attackers can target the endpoints too — which is why the "embedded security" model was developed.

Tip: You'll encounter Alice, Bob, and Eve throughout all of cryptography. Other common characters: Mallory (active attacker), Trent (trusted third party).