An Efficient CCA2-Secure Variant of the McEliece Cryptosystem in the Standard Model

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Recently, a few chosen-ciphertext secure (CCA2-secure) variants of the McEliece public-key encryption (PKE) scheme in the standard model were introduced. All the proposed schemes are based on encryption repetition paradigm and use general transformation from CPA-secure scheme to a CCA2-secure one. Therefore, the resulting encryption scheme needs separate encryption and has large key size compared to the original scheme, which complex public key size problem in the code-based PKE schemes. Thus, the proposed schemes are not sufficiently efficient to be used in practice. In this work, we propose an efficient CCA2-secure variant of the McEliece PKE scheme in the standard model. The main novelty is that, unlike previous approaches, our approach is a generic conversion and can be applied to any one-way trapdoor function (OW-TDF), the lowest-level security notion in the context of public-key cryptography, resolving a big fundamental and central problem that has remained unsolved in the past two decades.