Hi During work on the implementation of BIP151  I figured out that the current published proposal could be further optimized.
I wrote an overhauled BIP151 specification with some – partially radical – changes. Now it’s unclear to me if this should be published under a new BIP nr. or if it is acceptable to change the existing 151 proposal. If a new BIP number would be required, I think withdrawing BIP151 should be done (which somehow indicates we should alter 151). The only BIP151 implementation I’m aware of is the one from Armory . BCoins implementation has been removed . The new proposal draft is available here: https://gist.github.com/jonasschnelli/c530ea8421b8d0e80c51486325587c52 Major changes ============= - the encryption handshake no longer requires the v1 protocol, it’s a pure 32bytes-per-side „pseudorandom" key exchange that happens before anything else. - the multi message envelope has been removed. - a new NODE_ENCRYPTED service bit - the key derivation and what communication direction uses what key is now more specific - the length of a packet uses now a 3-byte integer with 23 available bits - introduction of short-command-ID (ex.: uint8_t 13 == INV, etc.) which result in some v2 messages require less bandwidth then v1 - rekeying doesn’t require a message and can be signaled in the most significant bit in the packet-size field Points that are in discussion and may be added to the BIP (or to a new one): Hybrid NewHope key exchange =========================== The current ECDH key exchange is vulnerable to Shor’s algorithm and is thus not considered quantum-safe. Following TORs approach  by adding a NewHope  key-exchange the handshake protocol would very likely make the encryption PQ safe with little costs. There is also a straight forward implementation  from the NewHope team that has been submitted to NIST PQC project. Inefficiency of ChaCha20Poly1305@openssh ======================================== The proposed AEAD could eventually be further optimized. ChaCha20Poly1305@openssh uses at least three rounds of ChaCha20 which eventually can be reduced to two (messages below <=64 bytes [inv, ping, pong,...] only require one round of ChaCha20, but two for the Poly1305 key and the message length encryption where the Poly1305 key chacha round „throws away“ 32 bytes). I would suggest that we don’t rehash discussions about the general concept of encrypting the traffic. This has already been discussed . I hope we can limit this thread to discuss further ideas for optimisation as well as technical details of the published proposal or its implementation.  https://github.com/bitcoin/bitcoin/pull/14032  https://github.com/goatpig/BitcoinArmory/pull/510  https://github.com/bcoin-org/bcoin/commit/41af7acfd68b0492a6442865afd439300708e662  https://gitweb.torproject.org/user/isis/torspec.git/plain/proposals/XXX-newhope-hybrid-handshake.txt?h=draft/newhope  https://eprint.iacr.org/2015/1092  https://github.com/newhopecrypto/newhope  https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-February/013565.html  https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-June/012826.html Thanks
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