An information-theoretic security analysis of quantum string sealing

A quantum sealing protocol is a quantum cryptographic protocol that can detect unsealing of a message. It is known that quantum bit sealing is insecure. However, this does not imply that quantum string sealing is also insecure. So the possibility of quantum string sealing has been studied. In this paper, we propose a quantum sealing protocol and give an information theoretic analysis. We also show that our protocol is almost optimal for uniformly distributed inputs in the sense that the upper bound of information leaks almost matches the trivial lower bound.