From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Hristo Georgiev <hristo.metal@gmail.com>
Cc: WireGuard mailing list <wireguard@lists.zx2c4.com>
Subject: Re: Nonce in out-of-order messages
Date: Sun, 25 Aug 2019 09:56:48 -0600 [thread overview]
Message-ID: <CAHmME9rPiyV73jUF9p=nQ+_8JswON1usWbOKpaT6SavsOokpdA@mail.gmail.com> (raw)
In-Reply-To: <E6BE60A6-0A9F-4A45-9FCE-155410ECDC6F@gmail.com>
On Sun, Aug 25, 2019 at 9:36 AM Hristo Georgiev <hristo.metal@gmail.com> wrote:
>
> Hello
> I’m working on file transfer protocol inspired by Noise and Wireguard over UDP with static keys so the handshake pattern is going to be Noise_IK_25519_ChaChaPoly_BLAKE2s or KK. In general i’m trying to follow NoiseSocket spec but adapted to UDP and i was wondering where to place the ‘nonce’ into packet to extend the protocol as described into p.11.4 in NoiseProtocol spec http://www.noiseprotocol.org/noise.html#out-of-order-transport-messages . So I had a look into WireGuard implementation (which I use a lot in multiple sites, mostly on EdgeRouters)
> so what i found in noise.c line 445 message_decrypt:
>
> chacha20poly1305_decrypt(dst_plaintext, src_ciphertext, src_len,
> hash, NOISE_HASH_LEN,
> 0 /* Always zero for Noise_IK */, key))
>
> Correct me if I’m mistaken, I’m not C programer nor cryptographer, I think this zero here is the Nonce. If that’s the case what security sacrifices and the chance for replay attacks are?
> Would it be Ok if I also hardcode the Nonce to 0 in my implementation?
This isn't the nonce used as part of the transport object, but rather
a single encryption/decryption that happens with a unique key as part
of the handshake. It being zero is a natural consequence of the
protocol flow.
Don't hardcode a zero nonce in transport messages.
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next prev parent reply other threads:[~2019-08-25 16:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-24 10:05 Nonce in out-of-order messages Hristo Georgiev
2019-08-25 15:56 ` Jason A. Donenfeld [this message]
2019-09-01 8:10 ` Hristo Georgiev
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