Semantic Security and Indistinguishability in the Quantum World

Understand

At CRYPTO 2013, Boneh and Zhandry initiated the study of quantum-secure encryption.

• They proposed first indistinguishability definitions for the quantum world where the actual indistinguishability only holds for classical messages, and they provide arguments why it might be hard to achieve a stronger notion.
• In this work, we show that stronger notions are achievable, where the indistinguishability holds for quantum superpositions of messages.
• We investigate exhaustively the possibilities and subtle differences in defining such a quantum indistinguishability notion for symmetric-key encryption schemes.