What do you think is the role of monogamous entanglement in ensuring secrecy in quantum communication protocols?
In quantum key distribution (QKD), private messages are secured by two parties sharing a cryptographic key. In some QKD protocols, the two parties share an entangled state. By performing measurements on their part of the state, the key is generated. In theory, the two parties should always measure the same outcome when measuring their part of the entangled pair. The monogamy of quantum entanglement then makes sure that it's impossible for a third party to also be entangled to the shared state and having access to the key.