US 12,284,267 B2
Fully homomorphic encryption for fixed-point elements
Nir Drucker, Zichron Yaakov (IL); Guy Moshkowich, Nes Ziyona (IL); Tomer Pelleg, Haifa (IL); and Hayim Shaul, Kfar Saba (IL)
Assigned to International Business Machines Corporation, Armonk, NY (US)
Filed by International Business Machines Corporation, Armonk, NY (US)
Filed on Jan. 29, 2023, as Appl. No. 18/102,735.
Prior Publication US 2024/0275577 A1, Aug. 15, 2024
Int. Cl. H04L 9/00 (2022.01); H04L 9/06 (2006.01)
CPC H04L 9/008 (2013.01) [H04L 9/0618 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A computer-implemented method comprising:
receiving, as input, a ciphertext x representing a computational result of an approximated fully-homomorphic encryption (FHE) scheme, wherein ciphertext x comprises a combination of an underlying number m and an accumulated computational error e;
iteratively,
(i) performing a bit extraction operation to extract a current most significant bit (MSB) x′ of ciphertext x,
(ii) calculating accuracy parameters input precision α, output precision β associated with x′,
(iii) applying a step function to said extracted MSB x′, based, at least in part, on said calculated accuracy parameters α, β, to reduce or remove said accumulated computational error e and to return a clean MSB b, and
(iv) repeating steps (i)-(iii) for all bits included in said underlying number m; and
reconstructing and outputting, from all of said returned clean MSBs b, said number m,
wherein m has fewer bits than x.