US 12,388,621 B2
Cryptographic system, encryption device, decryption device, and key generation device
Katsuyuki Takashima, Tokyo (JP)
Assigned to MITSUBISHI ELECTRIC CORPORATION, Tokyo (JP)
Filed by Mitsubishi Electric Corporation, Tokyo (JP)
Filed on Feb. 2, 2023, as Appl. No. 18/163,485.
Application 18/163,485 is a continuation of application No. PCT/JP2020/035870, filed on Sep. 23, 2020.
Prior Publication US 2023/0179397 A1, Jun. 8, 2023
Int. Cl. H04L 29/06 (2006.01); G06F 21/00 (2013.01); H04L 9/06 (2006.01); H04L 9/08 (2006.01); H04L 9/30 (2006.01)
CPC H04L 9/0618 (2013.01) [H04L 9/0861 (2013.01); H04L 9/3066 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A cryptographic system to perform a cryptographic process in which a Richelot isogeny sequence φs includes a first starting point and a first end point, the first starting point being an abelian surface A0 and the first end point being an abelian surface As the abelian surface A0 being a first secret key and the abelian surface As being a first public key, the cryptographic system comprising:
processing circuitry configured to:
compute an abelian surface Am by transitioning the abelian surface As, which is the first public key, by a Richelot isogeny sequence φm generated by encoding a plaintext m, and set the abelian surface Am as a ciphertext; and
compute a Richelot isogeny φm with a second start point and a second end point, the second starting point being the abelian surface As, the abelian surface As being a second public key, and the second end point is the abelian surface Am, the abelian surface Am being the ciphertext, based on the Richelot isogeny sequence φs, the Richelot isogeny sequence φs bring a second secret key.