Keyed cryptographic (MAC)

UMAC & VMAC

Two universal-hash-based MACs from the early 2000s. UMAC by Black, Halevi, Krawczyk, Krovetz, and Rogaway (RFC 4418, 2006); VMAC by Krovetz and Dai (2007). When CPUs hit 32-bit and 64-bit multiply-add instructions, UMAC / VMAC briefly held the “fastest MAC in the world” crown. Today Poly1305 (portable) and GHASH (with CLMUL hardware) have taken that throne, and UMAC / VMAC live on mostly in legacy protocols.

How they differ

• UMAC , 32-bit-friendly: NH (Carter-Wegman style universal hash) feeding a stream cipher. Output: 32, 64, 96, or 128 bits.
• VMAC , 64-bit-tuned successor using a polynomial over F_p(2⁶¹ − 1). Same security philosophy as UMAC, much faster on 64-bit hardware.

At a glance

Where they show up today

• SSH , umac-64@openssh.com and umac-128@openssh.com as available HMACs.
• Cryptographic literature , foundational examples for universal-hash MAC analysis.
• Some embedded crypto libraries.

vs Poly1305 / GHASH

All three are Carter-Wegman style: a fast universal hash combined with a per-nonce key from a block cipher / stream cipher. Poly1305 beats UMAC on portable code (no hardware needed). GHASH beats everything on CPUs with CLMUL (since 2010 Intel SSE4.2 / AES-NI Westmere). UMAC / VMAC are the historical bridge.

References

• RFC 4418 , UMAC: Message Authentication Code using Universal Hashing
• VMAC project page (Krovetz)
• Poly1305 · GMAC