class Net::SSH::Transport::Kex::Curve25519Sha256

key-exchange algorithm. (defined in tools.ietf.org/html/draft-ietf-curdle-ssh-curves-06)
A key-exchange service implementing the “curve25519-sha256@libssh.org”

def compute_shared_secret(server_ecdh_pubkey)

compute shared secret from server's public key and client's private key 
def compute_shared_secret(server_ecdh_pubkey)
  pk = ::X25519::MontgomeryU.new(server_ecdh_pubkey)
  OpenSSL::BN.new(ecdh.diffie_hellman(pk).to_bytes, 2)
end

def digester 

def digester
  OpenSSL::Digest::SHA256
end

def ecdh_public_key_bytes

# string Q_C, client's ephemeral public key octet string 
def ecdh_public_key_bytes
  ecdh.public_key.to_bytes
end

def generate_key # :nodoc:

:nodoc: 
def generate_key # :nodoc:
  ::X25519::Scalar.generate
end