[Cfrg] HPKE, message lengths, and IND-CCA2
John Mattsson <john.mattsson@ericsson.com> Fri, 23 October 2020 08:53 UTC
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From: John Mattsson <john.mattsson@ericsson.com>
To: "cfrg@ietf.org" <cfrg@ietf.org>
Thread-Topic: HPKE, message lengths, and IND-CCA2
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Date: Fri, 23 Oct 2020 08:53:53 +0000
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Archived-At: <https://mailarchive.ietf.org/arch/msg/cfrg/67D-qlKwuGsGY_H_ImGoTWnGjnM>
Subject: [Cfrg] HPKE, message lengths, and IND-CCA2
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HI, While the theoretical IND-CCA2 game assumes that the attacker generates messages with a fixed lengths, this is not very realistic in reality where messages often has variable length. It would be good to inform the reader that the specified mechanism does nothing to hide the length of the encrypted message, and if this is a concern, the user needs to use a padding mechanism The draft could also e.g. suggest how to do padding, e.g. the bit padding mechanism combined with one of the padding policies from https://tools.ietf.org/html/draft-ietf-tls-esni-08 https://tools.ietf.org/html/rfc8467 Cheers, John
- [Cfrg] HPKE, message lengths, and IND-CCA2 John Mattsson
- Re: [Cfrg] HPKE, message lengths, and IND-CCA2 Christopher Wood