[bitcoin-dev] p2p authentication and encryption BIPs

Jonas Schnelli dev at jonasschnelli.ch
Wed May 25 09:36:24 UTC 2016

>> Good point.
>> I have mentioned this now in the BIP but I think the BIP should allow
>> message > 16 MiB.
>> I leave the max. message length up to the implementation while keeping
>> the 4 byte length on the protocol level.
> I expect the implementation defined max size to work (SSH 2.0 does this
> after all), but I want to make sure my suggestion is understood
> completely.
> There is a length field for the encrypted data, and length field(s)
> inside of the encrypted data to indicate the length of the plaintext
> Bitcoin messages. I am suggesting that the outter (encrypted) length
> field be reduced, which will _not limit_ the length of Bitcoin
> messages. For example, if a 1 GiB Bitcoin message needed to be sent
> and the encrypted length field was 3 bytes - the sender is forced to
> send a minimum of 64 MACs for this message. The tradeoff is allowing
> the receiver to detect malformed data sooner and have a lower max
> buffering window **against** slightly higher bandwidth and CPU
> requirements due to the additional headers+MACs (the CPU requirements
> should primarily be in "finalizing each Poly1305").

Okay. Got your point.
The current BIPs assumption is that an encrypted package/message can
contain 1..n bitcoin messages (a single bitcoin message distributed over
multiple encrypted messages/packages was not specified).

But right, this could make sense.
Let me think this through....

> An alternative way to think about the suggestion is tunnelling Bitcoin
> messages over TLS or SSH. TLS 1.2 has a 2-byte length field and SSH 2.0
> a 4-byte length field, but neither prevents larger Bitcoin messages from
> being tunnelled; the lengths are independent.

TLS/SSH tunneling is already possible with third party software like
Also there is promising projects that would encrypt the traffic "on a
deeper layer" (see CurveCP).

I think what we want is a simple, openssl-independent traffic encryption
built into the core p2p layer.

IMO the risk of screwing up the implementation is moderate.

The implementation is not utterly-complex:
OpenSSH chacha20:


Sure. Before an implementation will be deployed to the endusers it will
require intense cryptoanalysis first.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: OpenPGP digital signature
URL: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/attachments/20160525/3aed6567/attachment.sig>

More information about the bitcoin-dev mailing list