Re: [TLS] Constraining ECH to HKDF-based HPKE ciphersuites
Christopher Patton <cpatton@cloudflare.com> Mon, 17 August 2020 21:55 UTC
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From: Christopher Patton <cpatton@cloudflare.com>
Date: Mon, 17 Aug 2020 14:55:37 -0700
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To: Martin Thomson <mt@lowentropy.net>
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Subject: Re: [TLS] Constraining ECH to HKDF-based HPKE ciphersuites
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Hi Martin,
> Or maybe just running the HPKE KDF with a fixed input.
Do you mean something like this? Let `config_digest = KDF.extract("some
salt", "some label", config)`, where `config` is the ECH configuration?
Unless I've missed something critical, you don't need any sort of preimage
> resistance for this, it's only for identification purposes.
>
The manner in which `config_digest` is computed could be significant to
"don't stick out", depending on how you define this property. For example,
one requirement for the hash function might be that it is one-way.
Chris P.
- [TLS] Constraining ECH to HKDF-based HPKE ciphers… Christopher Wood
- Re: [TLS] Constraining ECH to HKDF-based HPKE cip… Martin Thomson
- Re: [TLS] Constraining ECH to HKDF-based HPKE cip… Christopher Patton
- Re: [TLS] Constraining ECH to HKDF-based HPKE cip… Martin Thomson
- Re: [TLS] Constraining ECH to HKDF-based HPKE cip… Christopher Patton
- Re: [TLS] Constraining ECH to HKDF-based HPKE cip… Christopher Wood
- Re: [TLS] Constraining ECH to HKDF-based HPKE cip… Martin Thomson
- Re: [TLS] Constraining ECH to HKDF-based HPKE cip… Christopher Patton