Apparatus for performing threshold design on secret key and method thereof

Patent metadata

Field	Value
Publication number	US-11201735-B2
Application number	US-202016791297-A
Country	US
Kind code	B2
Filing date	Feb 14, 2020
Priority date	Feb 15, 2019
Publication date	Dec 14, 2021
Grant date	Dec 14, 2021

Abstract

An encryption method is disclosed. The encryption method includes calculating a secret key from a ring as a set closed for addition and multiplication defined between elements, generating a plurality of partial secret keys using the calculated secret key and a random matrix, and distributing the plurality of generated partial secret keys.

First claim

What is claimed is:

1. An encryption method comprising:
calculating a secret key from a ring as a set closed for addition and multiplication defined between elements;
generating a plurality of partial secret keys using the calculated secret key and a random matrix;
generating a public key using the secret key;
generating a homomorphic ciphertext using the generated public key, the homomorphic ciphertext can be operated and calculated without decryption;
distributing the plurality of generated partial secret keys and the homomorphic ciphertext;
collecting partial decipher texts each generated by applying the homomorphic ciphertext to a partial secret key among the plurality of partial secret keys equal to or greater than a threshold; and
decrypting a plain text corresponding to the homomorphic ciphertext using the collected partial decipher texts equal to or greater than the threshold.

2. The encryption method as claimed in claim 1 , wherein
the random matrix has a number of rows corresponding to a number of users and a number of columns corresponding to a threshold.

3. The encryption method as claimed in claim 1 , wherein
the random matrix has a number of rows corresponding to a number of users and a number of keys to be distributed to each user and a number of columns corresponding to a threshold.

4. The encryption method as claimed in claim 3 , wherein
in the distributing, the plurality of distribution secret keys is distributed to each user by the number of keys.

5. The encryption method as claimed in claim 1 , wherein
in the generating, a plurality of random values is generated and the plurality of partial secret keys are generated by applying a vector matrix including the plurality of random values and the secret key to the random matrix.

6. The encryption method as claimed in claim 1 , further comprising:
collecting partial secret keys equal to or greater than a threshold, among the plurality of partial secret keys; and
recovering the secret key using the collected partial secret keys.

7. An arithmetic operation device comprising:
a memory configured to store at least one instruction; and
a processor configured to execute the at least one instruction,
wherein the processor, by executing the at least one instruction, calculates a secret key from a ring as a set closed for addition and multiplication defined between elements, generates a plurality of partial secret keys using the calculated secret key and a random matrix, generates a public key using the secret key, generates a homomorphic ciphertext using the generated public key, the homomorphic ciphertext can be operated and calculated without decryption, distributes the plurality of generated partial secret keys and the homomorphic ciphertext, collects partial decipher texts each generated by applying the homomorphic ciphertext to a partial secret key among the plurality of partial secret keys equal to or greater than a threshold and decrypts a plain text corresponding to the homomorphic ciphertext using the collected partial decipher texts equal to or greater than the threshold.

8. The arithmetic operation device as claimed in claim 7 , wherein
the processor generates a plurality of random values and generate the plurality of partial secret keys by applying a vector matrix including the plurality of random values and the secret key to the random matrix.

9. The arithmetic operation device as claimed in claim 7 , wherein
the random matrix has a number of rows corresponding to a number of users and a number of secret keys to be distributed for each user and a number of columns corresponding to a threshold, and the processor is configured to distribute the plurality of partial secret keys to each user.

Assignees

• Crypto Lab Inc
• Seoul Nat Univ R&Db Foundation

Inventors

• Cheon Jung Hee
• Jeong Jinhyuck
• Yhee Donggeon
• Cho Wonhee

Classifications

• H04L2209/24

  Key scheduling, i.e. generating round keys or sub-keys for block encryption · CPC title

• H04L9/0825 Primary

  using asymmetric-key encryption or public key infrastructure [PKI], e.g. key signature or public key certificates · CPC title

• H04L9/0618

  Block ciphers, i.e. encrypting groups of characters of a plain text message using fixed encryption transformation · CPC title

• H04L9/0819

  Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) (network architectures or network communication protocols for key distribution in a packet data network H04L63/062) · CPC title

• H04L9/085 Primary

  Secret sharing or secret splitting, e.g. threshold schemes · CPC title