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RE: SHA-256/384/512
Thanks for your feedback.
A related question about AES counter mode for encryption with AES-MAC for
authentication...
The slides proposed AES counter mode so data blocks could be encrypted in
parallel (unlike CBC, which requires the results from block N before
beginning encryption of block N+1). If I remember correctly, MAC
authentication would be encrypting every block via AES using some sort of
feedback, and using the final ciphertext as the authentication data.
Something like:
Hash[n+1] = Block[n+1] ^ Encrypt(Data = Block[n+1],Key = Hash[n])
AES-MAC == Hash[Last Block]
This means AES-MAC for authentication would have a similar performance to
AES-CBC for encryption, so there wouldn't be an overall performance
advantage in using AES counter mode with parallel hardware for encryption.
Is this correct?
Best Regards,
Joseph D. Harwood
jharwood@vesta-corp.com
www.vesta-corp.com
> -----Original Message-----
> From: smb@research.att.com [mailto:smb@research.att.com]
> Sent: Friday, March 02, 2001 6:07 PM
> To: Joseph D. Harwood
> Cc: Ipsec
> Subject: Re: SHA-256/384/512
>
>
> In message
> <NDBBIBHFGLMFGJLIBOBMIEJICCAA.jharwood@vesta-corp.com>, "Joseph D. H
> arwood" writes:
> >This is a multi-part message in MIME format.
> >
> >------=_NextPart_000_0016_01C0A342.630F73E0
> >Content-Type: text/plain;
> > charset="iso-8859-1"
> >Content-Transfer-Encoding: 7bit
> >
> >In looking over Steve Kent's slides from the IPsec working group
> meeting on
> >"IPsec Enhancements for High Speed Networks," it discusses only
> AES-MAC for
> >authentication. Does this mean HMAC-SHA256 (/384/512) are not being
> >considered?
> >
> At the moment, it's easier to build very fast hardware encryptors than
> very fast hardware SHA chips. No one is deprecating HMAC; it's just
> that it's not the best choice for very high speed nets.
>
>
> --Steve Bellovin, http://www.research.att.com/~smb
>
>
>
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