  The model of the quantum protocols sealing a classical bit is studied. It is
shown that there exist upper bounds on its security. For any protocol where the
bit can be read correctly with the probability $\alpha $, and reading the bit
can be detected with the probability $\beta $, the upper bounds are $% \beta
\leqslant 1/2$ and $\alpha +\beta \leqslant 9/8$.
