Remember GCM
Full name: Galois/Counter Mode
Memory aid: Galois checks integrity while the Counter encrypts.
Key, nonce, and authentication-tag handling are all security-critical.
Study area: Cryptography & trust · Batch 8
Relevant study for: CompTIA Security+ SY0-701 · ISC2 CISSP 2024 outline · ISC2 SSCP · CompTIA SecurityX · Cybersecurity Architect SC-100 · ISC2 CCSP · Security, Compliance, and Identity Fundamentals SC-900
Practice with exam flashcards →Cybersecurity & Identity / Knowledge library
GCM — Galois/Counter Mode
Provides authenticated encryption using counter-mode encryption and a polynomial authenticator.
Why learn GCM — Galois/Counter Mode?
Provides authenticated encryption using counter-mode encryption and a polynomial authenticator.
Where it came from
Key, nonce, and authentication-tag handling are all security-critical.
- Memory aid (a learning cue, not the expansion): Galois checks integrity while the Counter encrypts.
Build your understanding
Work through these exercises in order. Try the task before opening a reference.
- Without looking, expand GCM: Galois/Counter Mode.
- Recall this memory aid: Galois checks integrity while the Counter encrypts.
- Explain the practical use: Provides authenticated encryption using counter-mode encryption and a polynomial authenticator.
- Explain this distinction: Key, nonce, and authentication-tag handling are all security-critical.
- Identify GCM in a device specification, architecture diagram, or system inventory.
Documentation and sources
- IETF RFC 5116 (www.rfc-editor.org)