Error Correction for FrodoKEM Using the Gosset Lattice
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We consider FrodoKEM, a lattice-based cryptosystem based on LWE, and propose a new error correction mechanism to improve its performance. Our encoder maps the secret key block-wise into the Gosset lattice E_8. We propose two sets of parameters for our modified implementation. Thanks to the improved error correction, the first implementation outperforms FrodoKEM in terms of concrete security by 10 to 13 bits by increasing the error variance; the second allows to reduce the bandwidth by 7% by halving the modulus q. In both cases, the decryption failure probability is improved compared to the original FrodoKEM. Unlike some previous works on error correction for lattice-based protocols, we provide a rigorous error probability bound by decomposing the error matrix into blocks with independent error coefficients.
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