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OMAC/CMAC

One-Key Cipher-Based Message Authentication Code as defined in NIST SP 800-38B. Provides provably secure message authentication using a single key with any block cipher.

Properties

Property	Value
Category	Message Authentication
Sub-category	Block Cipher MAC
Security status	🛡️ Secure
Complexity	Intermediate
Inventor	Tetsu Iwata, Kaoru Kurosawa
Year	2003
Origin	🇯🇵 Japan
Source	algorithms/mac/omac.js

Parameters

Parameter	Supported values
MAC sizes	16 bytes (128 bits)

Capabilities

Flag	Value
NeedsKey	Yes

Security

Status: 🛡️ Secure

No vulnerabilities are recorded for this implementation.

Documentation

• NIST SP 800-38B - CMAC Specification
• RFC 4493 - The AES-CMAC Algorithm

References

• OpenSSL CMAC Implementation
• Bouncy Castle CMAC
• Python Cryptography CMAC

Test vectors

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

Vector 1 — NIST SP 800-38B Example 1 - Empty Message

Field	Value
key	2b7e151628aed2a6abf7158809cf4f3c
input	(empty)
expected	bb1d6929e95937287fa37d129b756746

Vector 2 — NIST SP 800-38B Example 2 - Single Block

Field	Value
key	2b7e151628aed2a6abf7158809cf4f3c
input	6bc1bee22e409f96e93d7e117393172a
expected	070a16b46b4d4144f79bdd9dd04a287c

Vector 3 — NIST SP 800-38B Example 3 - Multi Block

Field	Value
key	2b7e151628aed2a6abf7158809cf4f3c
input	6bc1bee22e409f96e93d7e117393172a ae2d8a571e03ac9c9eb76fac45af8e51 30c81c46a35ce411
expected	dfa66747de9ae63030ca32611497c827

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