[noise] expected length of messages during handshake

Justin Cormack justin at specialbusservice.com
Wed Nov 1 12:54:05 PDT 2017

On 1 November 2017 at 19:51, David Wong <davidwong.crypto at gmail.com> wrote:
>> It is assumed you have a transport layer underneath that ReadMessage
>> talks to.
> Yes, but this transport layer doesn't tell you how long a Noise
> ciphertext is. See my example.

Then you need an additional transport layer.

>> You might not be using tcp. TCP usually needs a length, yes, although
>> you can also pad all the messages to fixed lengths instead. Other transports
>> already may include framing information.
> UDP doesn't fix the problem, see my example again where two
> concatenated Noise messages can fit in one UDP message.

seqpacket sockets fix the problem, for example but only for local communication,
or tcp with a framing layer (eg 16 bit message lengths followed by
data sections).

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