How to Build Unconditionally Secure Quantum Bit Commitment Protocols

摘要

The ``impossibility proof'' on unconditionally secure quantum bit commitmentis critically analyzed. Many possibilities for obtaining a secure bitcommitment protocol are indicated, purely on the basis of two-way quantumcommunications, which are not covered by the impossibility proof formulation.They are classified under six new types of protocols, with security proofs forspecific examples on four types. Reasons for some previously failed attempts atobtaining secure protocols are also indicated.