Chosen-Ciphertext Security from Subset Sum

We construct a public-key encryption (PKE) scheme whose
security is polynomial-time equivalent to the hardness of the Subset Sum
problem. Our scheme achieves the standard notion of indistinguishability
against chosen-ciphertext attacks (IND-CCA) and can be used to
encrypt messages of arbitrary polynomial length, improving upon a previous
construction by Lyubashevsky, Palacio, and Segev (TCC 2010)
which achieved only the weaker notion of semantic security (IND-CPA)
and whose concrete security decreases with the length of the message
being encrypted.
At the core of our construction is a trapdoor technique which originates
in the work of Micciancio and Peikert (Eurocrypt 2012).