Uncloneable Cryptography
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The no-cloning theorem asserts that, unlike classical information, quantum information cannot be copied. This seemingly undesirable phenomenon is harnessed in quantum cryptography. Uncloneable cryptography studies settings in which the impossibility of copying is a desired property, and achieves forms of security that are classically unattainable. The first example discovered and analyzed was in the context of cash. On the one hand, we want users to hold the cash; on the other hand, the cash should be hard to counterfeit. Quantum money uses variants of the no-cloning theorem to make counterfeiting impossible. In the past decade, this field developed in various directions: several flavors of quantum money, such as classically verifiable, locally verifiable, semi-quantum, quantum coins, and quantum lightning were constructed. New uncloneable primitives were introduced, such as uncloneable signatures, quantum copy protection for classical software, pseudorandom states, and several uncloneable forms of encryption. This work is a gentle introduction to these topics.
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