Ludwig, Hannes,

The differences with RFC7250 are twofold:
 1. The raw public keys are not exchanged in the handshake sequence. Even with 
cached info (RFC7924), a fingerprint of the certificate (or raw public key) is 
exchanged. Also, a ClientVerify message is needed if mutual authentication is 
required (which is automatic with 3ECDH). These extra elements add to the size 
of the handshake exchange. They also identify the sender (whereas my draft 
encrypts the client identity), which can be an issue if privacy of the session 
endpoints is important. 

 2. ECDH cannot be used as a raw public key; instead ECDSA or EdDSA is needed. 
But ECDH is also needed if the handshake includes perfect forward secrecy 
(highly recommended/mandatory, depending on usage). Therefore the client has to 
implement two algorithms and may need to implement fast versions of both of 
them to reduce latency in session establishment. Using 3ECDH, the client only 
needs a single algorithm; if EdDSA is needed anyway (e.g. for code signing), 
then a slow version may be used which saves code-space and data-space. 
-- 
Tony

> -----Original Message-----
> From: Ace [mailto:[email protected]] On Behalf Of Ludwig Seitz
> Hi Tony,
> 
> could you explain the differences between your draft and the (D)TLS
> handshake with raw public keys (https://tools.ietf.org/html/rfc7250)?
> 
> /Ludwig
> https://www.ietf.org/mailman/listinfo/ace

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