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From: Jonas Schnelli <dev@jonasschnelli.ch>
To: Elichai Turkel <elichai.turkel@gmail.com>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] New BIP - v2 peer-to-peer message transport protocol
Date: Mon, 17 Jun 2019 18:20:32 +0200	[thread overview]
Message-ID: <76890B69-2004-41C4-B4E7-0C5D070142C3@jonasschnelli.ch> (raw)
In-Reply-To: <CALN7hCKheiE374S6wOMJSTufmuQFxa-d_0x_aJbEPT=KuDc0nw@mail.gmail.com>

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Hi Elichai

> About the nonce being 64bit. (rfc7539 changed it to 96bit, which djb later calls xchacha)
> 
> You suggest that we use the "message sequence number" as the nonce for Chacha20, Is this number randomly generate or is this a counter?
> And could it be reseted without rekeying?

The in BIP324 (v2 message transport protocol) proposed AEAD, ChaCha20Poly1305@Bitcoin [1], uses a „message sequence number“. There is no such thing as random nonce described in the BIP (hence the term „sequence number“). The message sequence number starts with 0 and the max traffic before a rekey must occur is 1GB. A nonce/key reuse is conceptually impossible (of course implementations could screw up at this point).

Using XChaCha20 with the possibility of a random nonce could be done, but I don’t see a reason to use it in our case since the usage of a sequence number as nonce seems perfectly save.

[1] https://gist.github.com/jonasschnelli/c530ea8421b8d0e80c51486325587c52#chacha20-poly1305bitcoin-cipher-suite

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  reply	other threads:[~2019-06-17 16:26 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-17  2:06 [bitcoin-dev] New BIP - v2 peer-to-peer message transport protocol Elichai Turkel
2019-06-17 16:20 ` Jonas Schnelli [this message]
2019-06-17 17:13   ` Elichai Turkel

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