US 12,381,736 B2
Cipher system, encryption apparatus, decryption apparatus, method, and program
Keita Kusagawa, Tokyo (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 18/553,346
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed Apr. 15, 2021, PCT No. PCT/JP2021/015630
§ 371(c)(1), (2) Date Sep. 29, 2023,
PCT Pub. No. WO2022/219785, PCT Pub. Date Oct. 20, 2022.
Prior Publication US 2024/0187246 A1, Jun. 6, 2024
Int. Cl. H04L 9/32 (2006.01)
CPC H04L 9/3242 (2013.01) [H04L 9/3263 (2013.01)] 3 Claims
OG exemplary drawing
 
1. A cipher system that performs encryption and decryption, the cipher system comprising:
a public key encryption scheme comprising a tag-based encryption (TBE) scheme comprising algorithms GenTBE, EncTBE, and DecTBE; a weak commitment scheme (wCom) comprising the following algorithms Init, S, and R; and a message authentication code scheme (MAC) comprising algorithms T and V; and
one or more information processing devices each including a memory and a processor configured to:
using a security parameter as κ, generate an encryption key ekTBE and a decryption key dkTBE by a key generation algorithm GenTBE(I), generate a common parameter pub by an initialization algorithm Init (1κ), and use the encryption key ekTBE and the common parameter pub as an encryption key ek of the public key encryption scheme and the decryption key dkTBE as a decryption key dk of the public key encryption scheme;
generate a random number r, a commitment com, and a decommitment dec by a sender algorithm S (1κ, pub), generate a ciphertext c by an encryption algorithm EncTBE (ekTBE, com, (m, dec)) using a plaintext to be encrypted as m, generate a tag σ by a MAC generation algorithm T (r, c), and use the commitment com, the ciphertext c, and the tag σ as a ciphertext ct of the public key encryption scheme; and
parse the ciphertext ct into the commitment com, the ciphertext c, and the tag σ, generate a plaintext m and a decommitment dec by a decryption algorithm DecTBE (dkTBE, com, c), verify whether committing to a random number value r has succeeded by a receiver algorithm R (pub, com, dec), and verify the tag σ by a verification algorithm V (r, c, a) in a case where the committing has succeeded.