Poor Mitch. The core of this sounds like another variant of the Mig-in-the-middle attack. Page 126 (page 10 of the PDF) from RJA’s Security Engineering being

Poor Mitch. The core of this sounds like another variant of the Mig-in-the-middle attack. Page 126 (page 10 of the PDF) from RJA’s Security Engineering being my reference... https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch4-dec18.pdf https://www.cl.cam.ac.uk/~rja14/Papers/SEv3-ch4-dec18.pdf