'Used by TLSBox to initiate the SSL handshake.
@param certificate: a L{twisted.internet.ssl.PrivateCertificate} for
use locally.
@param verifyAuthorities: L{twisted.internet.ssl.Certificate} instances
representing certificate authorities which will verify our peer.'

def _startTLS(self, certificate, verifyAuthorities):

    self.hostCertificate = certificate
    self._justStartedTLS = True
    if (verifyAuthorities is None):
        verifyAuthorities = ()
    self.transport.startTLS(certificate.options(*verifyAuthorities))
    stlsb = self._startingTLSBuffer
    if (stlsb is not None):
        self._startingTLSBuffer = None
        for box in stlsb:
            self.sendBox(box)
