There is no need for exchange of blinding factors. The mailing list message https://lists.launchpad.net/mimblewimble/msg00091.html https://lists.launchpad.net/

There is no need for exchange of blinding factors. The mailing list message https://lists.launchpad.net/mimblewimble/msg00091.html https://lists.launchpad.net/mimblewimble/msg00091.html explains how any possible multi-party transaction can be done safely without exchanging blinding factors.