DataTerminology.comNEW
An authenticated encryption mode combining AES counter mode with Galois field authentication for fast, parallelizable confidentiality and integrity.
DESCRIPTION
AES-GCM is an AEAD mode that pairs AES in counter mode with a polynomial MAC over a Galois field to deliver both encryption and authentication. It is widely used in TLS, IPsec, and modern protocols for its speed and hardware acceleration. GCM’s parallelizable design yields low latency while supporting associated data for authenticated headers. Security requires unique nonces per key; misuse can degrade integrity. AES-GCM is a default choice for performance-sensitive secure communications.
ALTERNATIVE DEFINITIONS
NIST
This Recommendation specifies the Galois/Counter Mode (GCM), an authenticated encryption mode of operation for block ciphers.
Defines GCM formally as an AEAD mode for block ciphers.
Wikipedia
Galois/Counter Mode (GCM) is a mode of operation for symmetric key cryptographic block ciphers that is widely adopted for its efficiency and performance.
Emphasizes efficiency and widespread adoption.
RELATED TERMS
Rijndael Authenticated Encryption Counter GMAC TLS Nonce Authentication Tag Counter Mode with CBC-MAC MAC WPA3
COMPETING TERMS
AES-CCM
RELATIONS
- Broader: Authenticated Encryption
KNOWLEDGE AREAS
Data Security Software Engineering Infrastructure Data Privacy & Compliance Mathematics
TARGET AUDIENCE
Security Architect Cybersecurity Engineer Chief Information Security Officer Software Developer Cloud Architect
EXTERNAL SOURCES
- Wikipedia - Galois/Counter Mode
- NIST - Authoritative GCM specification
- OpenSSL - API docs for AES-GCM
- IETF - TLS AES-GCM cipher suites
TOP QUESTIONS
Why is AES-GCM preferred in TLS and modern protocols?
It delivers high performance, parallelizable authenticated encryption, and hardware acceleration, making it ideal for secure communications at scale.
Category: Relevancy
What is AEAD and how does AES-GCM implement it?
AEAD provides simultaneous confidentiality and integrity; AES-GCM uses CTR for encryption and a Galois field MAC for authentication.
Category: Concept
What is the biggest risk when using AES-GCM?
Nonce reuse with the same key seriously undermines integrity and confidentiality; strict nonce management is crucial.
Category: Risk
How does AES-GCM compare to AES-CCM?
GCM is generally faster and more parallelizable, while CCM can be simpler but less performant; both provide AEAD guarantees.
Category: Alternatives
Does AES-GCM support associated data?
Yes, you can authenticate headers or metadata without encrypting them, preserving integrity for context.
Category: Capability
Where is AES-GCM commonly used?
TLS, QUIC, IPsec, SSH, and various storage and messaging systems rely on AES-GCM for secure encryption.
Category: UseCase
How to test AES-GCM implementations?
Use NIST test vectors, verify tag computation, check nonce uniqueness, and cross-validate against vetted libraries.
Category: Testing
What is a misunderstanding about AES-GCM?
Some assume authentication guarantees remain despite nonce reuse; in reality, reuse can catastrophically break security.
Category: Misunderstanding
What are implementation best practices for AES-GCM?
Use unique nonces, constant-time code, hardware acceleration if available, and robust error handling for tag verification failures.
Category: BestPractices