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[TLS] Re: Composite ML-DSA

Peter Gutmann <pgut001@cs.auckland.ac.nz> Wed, 15 April 2026 14:22 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: Muhammad Usama Sardar <muhammad_usama.sardar@tu-dresden.de>, Filippo Valsorda <filippo@ml.filippo.io>
Thread-Topic: [TLS] Re: Composite ML-DSA
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Date: Wed, 15 Apr 2026 14:22:17 +0000
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Subject: [TLS] Re: Composite ML-DSA
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Muhammad Usama Sardar <muhammad_usama.sardar@tu-dresden.de> writes:

>Independent of that, that's not my read of this subthread. I don't see anyone
>other than David A to be in such strong position of "hell no."

Well I'll certainly add a +1 to it, for exactly the reasons given.  Throughout
all of crypto implementation history, signatures have been done with a single
signing key, and crypto libraries are built around that all the way up and
down the stack.  Having to store and apply two keys at the same time will, as
Filippo pointed out, propagate throughout the entire library.  Just look at,
well, literally every crypto API ever, the signing function uses *the* signing
key, not "one of a set of signing keys", and everything that calls down to it
also uses *the* signing key.

Peter.

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