Generalized Quantum Shannon Impossibility for Quantum Encryption. (arXiv:1801.03656v1 [cs.IT])

The famous Shannon impossibility result says that any encryption scheme with
perfect secrecy requires a secret key at least as long as the message. In this
paper we prove its quantum analogue with imperfect secrecy and imperfect
correctness. We also provide a systematic study of information-theoretically
secure quantum encryption with two secrecy definitions.

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