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GMAC

Galois Message Authentication Code as defined in NIST SP 800-38D. Authentication component of GCM mode using Galois Field arithmetic.

Properties

Property	Value
Category	Message Authentication
Sub-category	GMAC
Security status	🛡️ Secure
Complexity	Advanced
Inventor	NIST
Year	2007
Origin	🇺🇸 United States
Source	algorithms/mac/gmac.js

Parameters

Parameter	Supported values
MAC sizes	16 bytes (128 bits)

Capabilities

Flag	Value
NeedsKey	Yes
NeedsNonce	Yes

Security

Status: 🛡️ Secure

No vulnerabilities are recorded for this implementation.

Documentation

• NIST SP 800-38D - GCM Specification
• RFC 5288 - AES Galois Counter Mode

References

• Intel PCLMULQDQ Instruction
• Bouncy Castle GCM/GMAC
• OpenSSL GMAC Implementation

Test vectors

5 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Botan Test Vector 1 - Empty input

Field	Value
key	00000000000000000000000000000000
nonce	000000000000000000000000
input	(empty)
expected	58e2fccefa7e3061367f1d57a4e7455a

Vector 2 — Botan Test Vector 2 - 16-byte zero input

Field	Value
key	00000000000000000000000000000000
nonce	000000000000000000000000
input	00000000000000000000000000000000
expected	21c2eb20cd2214dbdf34c9b82ecb7ed2

Vector 3 — AES-128 GMAC - 20-byte message (node AES-128-GCM, empty plaintext)

Field	Value
key	010e1b2835424f5c697683909daab7c4
nonce	020f1c293643505d6a778491
input	03101d2a3744515e6b7885929facb9c6d3e0edfa
expected	be845653884a7a35f9d79b6fd26134cf

Vector 4 — AES-192 GMAC - 33-byte message (node AES-192-GCM, empty plaintext)

Field	Value
key	04111e2b3845525f6c798693a0adbac7d4e1eefb0815222f
nonce	05121f2c394653606d7a8794
input	0613202d3a4754616e7b8895a2afbcc9 d6e3f0fd0a1724313e4b5865727f8c99 a6
expected	4afc622c01f284717c67be13aa35456b

Vector 5 — AES-256 GMAC - 64-byte message (node AES-256-GCM, empty plaintext)

Field	Value
key	0714212e3b4855626f7c8996a3b0bdcad7e4f1fe0b1825323f4c596673808d9a
nonce	0815222f3c495663707d8a97
input	091623303d4a5764717e8b98a5b2bfcc d9e6f3000d1a2734414e5b6875828f9c a9b6c3d0ddeaf704111e2b3845525f6c 798693a0adbac7d4e1eefb0815222f3c
expected	43bd7ac4315954058dfc36d6e5e2d116

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