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Re: [TLS] Merkle Tree Certificates

Bas Westerbaan <bas@cloudflare.com> Wed, 07 June 2023 08:51 UTC

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From: Bas Westerbaan <bas@cloudflare.com>
Date: Wed, 07 Jun 2023 10:51:12 +0200
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To: Ilari Liusvaara <ilariliusvaara@welho.com>
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Subject: Re: [TLS] Merkle Tree Certificates
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>
> I mean, is there a cryptographic reason for it?


No.


> (However, absent cryptographic reasons, this all is way premature.)
>

Indeed. We like to have a concrete proposal, but thinking through these
details is premature at this point.

[snip] What that in effect does
> is to make it much more difficult to exploit chosen-prefix collisions in
> hash function.



However, that requirement holds irrespective of the hash function used,

and it has in fact been held for SHA-256 (regardless of there not being
> any known even remotely feasible attacks) instead of just being a dead
> letter from the past with much worse hash functions.
>

Ah, it would indeed be neat if we could design this, so that we do not
require (chosen prefix) collision resistance of the hash. I'd say it's nice
to have, but not a must. Tracking in
https://github.com/davidben/merkle-tree-certs/issues/45

Best,

 Bas

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