Security Trade-offs in Ancilla-Free Quantum Bit Commitment in the   Presence of Superselection Rules
  Security trade-offs have been established for one-way bit commitment in quant-ph/0106019. We study this trade-off in two superselection settings. We show that for an `abelian' superselection rule (exemplified by particle conservation) the standard trade-off between sealing and binding properties still holds. For the non-abelian case (exemplified by angular momentum conservation) the security trade-off can be more subtle, which we illustrate by showing that if the bit-commitment is forced to be ancilla-free an asymptotically secure quantum bit commitment is possible. 
D.P. DiVincenzo, J.A. Smolin and B.M. Terhal