SHARE GENERATION DEVICE, RESTORATION DEVICE, SECRET CALCULATION SYSTEM, SHARE GENERATION METHOD, RESTORATION METHOD, PROGRAM, AND RECORDING MEDIUM

• Main Authors: CHIDA, Koji, KIKUCHI, Ryo, IKARASHI, Dai
• Format: Patent
• Language: English; French; German
• Published: 05.05.2021
• Subjects: ADVERTISING; CODING OR CIPHERING APPARATUS FOR CRYPTOGRAPHIC OR OTHERPURPOSES INVOLVING THE NEED FOR SECRECY; CRYPTOGRAPHY; DISPLAY; EDUCATION; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PHYSICS; SEALS; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

A share [x]iof plaintext x in accordance with Shamir's secret sharing scheme is expressed by N shares [x0]i, ..., [xN-1]i, and each share generating device Aiobtains a function value ri= Pm(i(-))(Si) of a seed si, obtains a first calculated value ζi= λ(i, i(-))[xi(-)]i+riusing a Lagrange coefficient λ(i, i(-)), a share [xi(-)]i, and the function value ri, and outputs the first calculated value ζito a share generating device Ai(-). Each share generating device Aiaccepts a second calculated value ζi(+), obtains a third calculated value zi= λ(i, i(+))[xi]i+ζi(+)using a Lagrange coefficient λ(i, i(+)), a share [xi]i, and the second calculated value ζi(+), and obtains information containing the seed siand the third calculated value zias a share SSiof the plaintext x in secret sharing and outputs the share SSi.