  In a post-quantum world, where attackers may have access to full-scale
quantum computers, all classical password-based authentication schemes will be
compromised. Quantum copy-protection prevents adversaries from making copies of
existing quantum software; we suggest this as a possible approach for designing
post-quantum-secure password authentication systems. In this paper, we show an
implementation of quantum copy-protection for password verification on IBM
quantum computers. We also share our quantum computation results and analyses,
as well as lessons learned.
