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Date:   Fri, 15 Jan 2021 17:43:23 -0800
From:   Eric Biggers <>
To:     "Dey, Megha" <>
Cc:     Ard Biesheuvel <>,
        Herbert Xu <>,
        "David S. Miller" <>,
        Linux Crypto Mailing List <>,
        Linux Kernel Mailing List <>,,,,,,,,,,,,,
        Tony Luck <>,
Subject: Re: [RFC V1 3/7] crypto: ghash - Optimized GHASH computations

On Fri, Jan 15, 2021 at 04:14:40PM -0800, Dey, Megha wrote:
> > Hello Megha,
> > 
> > What is the purpose of this separate GHASH module? GHASH is only used
> > in combination with AES-CTR to produce GCM, and this series already
> > contains a GCM driver.
> > 
> > Do cores exist that implement PCLMULQDQ but not AES-NI?
> > 
> > If not, I think we should be able to drop this patch (and remove the
> > existing PCLMULQDQ GHASH driver as well)
> AFAIK, dm-verity (authenticated but not encrypted file system) is one use
> case for authentication only.
> Although I am not sure if GHASH is specifically used for this or SHA?
> Also, I do not know of any cores that implement PCLMULQDQ and not AES-NI.

dm-verity only uses unkeyed hash algorithms.  So no, it doesn't use GHASH.

- Eric

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