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SubjectRe: [PATCH] crypto: mark cts(cbc(aes)) as FIPS allowed
On 5 November 2018 at 10:18, Gilad Ben-Yossef <> wrote:
> Hi Stephan,
> On Mon, Nov 5, 2018 at 10:50 AM Stephan Mueller <> wrote:
>> Am Sonntag, 4. November 2018, 11:05:24 CET schrieb Gilad Ben-Yossef:
>> Hi Gilad,
>> > As per Sp800-38A addendum from Oct 2010[1], cts(cbc(aes)) is
>> > allowed as a FIPS mode algorithm. Mark it as such.
>> >
>> > [1]
>> There are several types of CTS approaches. Only three of those are listed in
>> the SP800-38A addendum. The source code only refers to some RFCs.
>> Did you check whether the CTS implementation matches one or more of the types
>> listed in the addendum? If yes, may I suggest to add a small statement in the
>> code noting this fact?
> Yes, AFAIK the software implements CBC-CS3 as described in the document.
> You have a very good point about this not document anywhere. I will
> send a patch.

I agree that it makes sense to document this.

> While we're at it, does someone find it useful if I implemented the
> other two modes?
> They are part of the standard as well, although I am not sure that in
> itself is sufficient cause.

Nope. The linux crypto API is not a general purpose cryptography
toolkit, it should only offer what we actually use in the kernel, or
we'll either end up with bitrot or with a disproportionate maintenance
burden for stuff nobody actually uses.

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