Authenticated Encryption

• Enables one-step construction from an Insecure to a Secure Channel
  • Authenticated Encryption is a “one-step” cryptographic primitive that simultaneously handles authentication & encryption.
• Authenticated Encryption with Associated Data (AEAD)
  • Provides Authenticity and Confidentiality
    • Authenticity: Ensures the message was created by the holder of the secret key and has not been altered by a single bit. If a message is tampered with, the decryption process will return a FAIL error rather than corrupt data.
    • Confidentiality: Ensures the payload (plaintext) is secret and unreadable to eavesdroppers.
  • What is “Associated Data”?
    • AD refers to data that needs to remain visible (unencrypted) but must be tamper-proof.
    • Example:
      • In a network packet, the IP header (destination address) must be visible, so routers know where to send it.
      • However, you want to ensure an attacker hasn’t changed the destination IP.
      • AEAD protects the integrity of this header (Associated Data) while encrypting the packet body (Payload).
• Implementation Examples
  • AES-GCM
    • ¹
  • AES-CCM
  • ChaCha20-Poly1305
  • (Encrypt-then-MAC)
    • ²

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Relevant Note(s):

Footnotes

1. https://en.wikipedia.org/wiki/File:GCM-Galois_Counter_Mode_with_IV.svg ↩

2. https://en.wikipedia.org/wiki/File:Authenticated_Encryption_EtM.png ↩