  Threshold schemes exist for many cryptographic primitives like signatures,
key derivation functions, and ciphers. At the same time, practical key exchange
protocols based on Diffie-Hellman (DH) or ECDSA primitives are not designed or
implemented in a threshold setting. In this paper, we implement popular key
exchange protocols in a threshold manner and show that this approach can be
used in practice. First, we introduce two basic threshold DH key agreement
schemes that provide enhanced security features in comparison with the classic
DH primitive: dealerless distributed key generation, threshold shared key
computation, and private key shares refreshing. We implemented the proposed DH
schemes within WireGuard protocol to demonstrate its effectiveness, efficiency,
and usability in practice. The open question is the security of the proposed
schemes and their instantiation from the elliptic curves used in key agreement
protocols: NIST curves, Russian GOST curves, and Curve25519. Second, we propose
an idea of implementing TLS in a threshold setting that can be used instead of
Keyless SSL/TLS technology, and provide the measurements of TLS key exchanges
based on threshold ECDSA. Even if we don't provide any formal definitions,
security analysis, and mathematical proofs, we believe that the ideas and
mechanisms suggested in this paper can be interesting and useful. The main
intention of the paper is to start discussions and raise awareness of the
challenges and problems arising when moving to threshold key exchange
protocols.
