phc-discussions - Re: [PHC] more woes, last woes

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Date: Tue, 15 Apr 2014 16:22:17 -0300 (BRT)
From: Marcos Antonio Simplicio Junior <mjunior@...c.usp.br>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] more woes, last woes

Hi. 

I tried to add some strengths to the Lyra2 algorithm. Please feel free to edit (or suggest modifications) if you feel it is not clear/fair enough. 

By the way, maybe some "weaknesses by design" should be explicitly mentioned too? I would list that Lyra2 is "only partially resistant against cache-timing attacks ", for example, in opposition to Catena's listed strength. 

BR, 

Marcos. 

----- Mensagem original -----

> De: "Thomas Pornin" <pornin@...et.org>
> Para: discussions@...sword-hashing.net
> Enviadas: Terça-feira, 15 de Abril de 2014 16:11:38
> Assunto: Re: [PHC] more woes, last woes

> On Tue, Apr 15, 2014 at 01:58:44PM -0500, Steve Thomas wrote:
> > Also it loses a lot of speed if you don't have AES-NI.

> Actually that one can be listed as a weakness, too. If a function
> uses
> some operation which relies on a specific hardware support (e.g.
> AES-NI), then you surely hope that the defender has access to it,
> because the attacker surely will. Using an AES-enhanced password
> hashing
> scheme when your actual hardware cannot run it efficiently equates to
> giving away a huge advantage to the attacker.

> It is a delicate balance: AES-NI looks like a good idea because an
> AES-optimized circuits are quite expensive for an ASIC/FPGA attacker,
> and also somewhat adverse to GPU, while the defender has AES-NI in
> his
> server. However, this holds only as long as the defender indeed has
> AES-NI in his server. This would not be true, for instance, on
> ARM-based
> server farms (that's the new fashion; it apparently saves a lot on
> energy and cooling).

> (Although there have been some announcements about soon-to-be ARM
> processors with AES opcodes. The situation is not completely clear.)

> --Thomas Pornin

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