It is not clear whether the special conditions under which it can be made to work are practical in the real world of noise, dirt, and imperfection in which most everything is required to function.
It may also be vulnerable to attacks specific to particular implementations and imperfections in the optical components of which the quantum cryptographic equipment is built.
A good understanding of these properties is needed before designing a secure channel, and before being able to assess its appropriateness of employment in a cryptographic protocol.
[citation needed] A universally composable authenticated channel can be built using digital signatures and a public key infrastructure.
[1] Universally composable confidential channels are known to exist under computational hardness assumptions based on hybrid encryption and a public key infrastructure.