Re: [TLS] WG interest in draft-chudov-cryptopro-cptls-02.txt

Greetings!

On Tue, 29 Nov 2005, Gregory S. Chudov wrote:

> I agree that it could be useful to add a paragraph, containing the reasoning
> for this.
>
> IMIT_GOST28147 is not an HMAC, it is basicly a form of GOST28147 cipher.
> To be robust to attacks based on timing and EMI analysis, one symmetric key
> should not  be used for large quantities of plaintext, so the key meshing
> algorithm
> from draft-popov-cryptopro-cpalgs-04.txt is applied.

Thank you, this paragraph provides enough information for me to understand
your design decision.

But the section 2 of draft-chudov-cryptopro-cptls-02.txt proposes two
cipher suites with GOSTR3411-based MAC. Is key meshing applied
for these cipher suites too or do they use usual HMAC? And what is MACed
data for them?

Thank you!

> This "abberation" can be rephrased in a following way: MACed_data[seq_num]
> is MACed, using the cipher state, produced by processing the previous record.
>
> Good luck!
>
> ----- Original Message ----- From: "Dmitry Belyavsky" <beldmit@cryptocom.ru>
> To: "Russ Housley" <housley@vigilsec.com>
> Cc: <tls@ietf.org>
> Sent: Tuesday, November 29, 2005 5:40 PM
> Subject: Re: [TLS] WG interest in draft-chudov-cryptopro-cptls-02.txt
>
>
> > Greetings!
> >
> ...
> >
> > What can you say about section 3.3 of draft-chudov-cryptopro-cptls-02.txt?
> > It describes a non-reasoned aberration from RFC 2246:
> >
> > ====================
> >   For all four cipher suites, the use of MAC is slighttly different
> >   from the one, described in section 6.2.3.1 of [TLS].  In [TLS], MAC
> >   is calculated from the following data:
> >
> >     MACed_data[seq_num] = seq_num +
> >                           TLSCompressed.type +
> >                           TLSCompressed.version +
> >                           TLSCompressed.length +
> >                           TLSCompressed.fragment;
> >
> >   These cipher suites use the same input for first record, but for each
> >   next record the input from all previous records is concatenated:
> >
> >     MACed_data[0] + ... + MACed_data[n]
> > ====================

-- 
SY, Dmitry Belyavsky (ICQ UIN 11116575)

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