NewHope without reconciliation

In this paper we introduce NewHope-Simple, a variant of the NewHope RingLWE-based key exchange that is using a straight-forward transformation from Ring-LWE encryption to a passively secure KEM (or key-exchange scheme). The main advantage of NewHopeSimple over NewHope is simplicity. In particular, it avoids the error-reconciliation mechanism originally proposed by Ding. The explanation of his method, combined with other tricks, like unbiasing the key following Peikert’s tweak and using the quantizer D4 to extract one key bit from multiple coefficients, takes more than three pages in the NewHope paper. The price for that simplicity is small: one of the exchanged messages increases in size by 6.25% from 2048 bytes to 2176 bytes. The security of NewHope-Simple is the same as the security of NewHope; the performance is very similar.

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