US 12,126,710 B2
Method for determining a cryptographic key, computer program, and data processing system
Vladimir Voloshinov, St. Gallen (CH); Gordey Lesovik, St. Gallen (CH); and Aleksei Pakhomchik, St. Gallen (CH)
Assigned to Terra Quantum AG, St. Gallen (CH)
Filed by Terra Quantum AG, St. Gallen (CH)
Filed on Jun. 30, 2022, as Appl. No. 17/854,493.
Claims priority of application No. 21183810 (EP), filed on Jul. 5, 2021.
Prior Publication US 2023/0027694 A1, Jan. 26, 2023
Int. Cl. H04L 9/06 (2006.01); G06N 10/60 (2022.01)
CPC H04L 9/0631 (2013.01) [G06N 10/60 (2022.01); H04L 9/0625 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A method for determining a cryptographic key, the method being carried out in a data processing system, the method comprising:
providing a plaintext and a ciphertext determined from the plaintext using the cryptographic key and a cryptographic procedure which comprises cryptographic operations;
for each cryptographic operation of the cryptographic procedure, providing at least one intermediate relation which comprises an intermediate equation and/or an intermediate inequality;
determining an optimization problem comprising
the plaintext and the ciphertext,
at least one optimization expression assigned to a round of the cryptographic procedure, and
optimization variables comprising state variables of the cryptographic procedure and a cryptographic key variable,
wherein the at least one optimization expression is determined from the at least one intermediate relation and comprises at least one preceding state variable assigned to a preceding round; and
solving the optimization problem and determining the cryptographic key from an optimizing value of the cryptographic key variable, wherein the optimization problem is at least partially solved in a quantum processing device of the data processing system.