According to various embodiments, a method for code-based generation of a key pair for asymmetric cryptography is described including generating a private key defining a linear code, determining a parity check or generator matrix for the linear code, blinding a sub-matrix of the parity check or generator matrix, generating a blinded inverse matrix by inverting the blinded sub-matrix or by inverting a quadratic matrix contained in the blinded sub-matrix, de-blinding the blinded inverse matrix to generate an inverse matrix and generating a public key for the private key using the inverse matrix.

Bitcoins and the underlying blockchain technology are one of the main innovations in building decentralized applications. The effects of quantum computing on this technology are analyzed in general. Provided herein are effective solutions to address security vulnerabilities in a blockchain-based system that can be exploited by a quantum attacker.

The present disclosure relates to methods of mining a block of a distributed ledger. The methods include: receiving a block to be mined, the block including a header hash and a plurality of transactions; creating a first signature based on a first function, where inputs to the first function include the header hash and the plurality of transactions; and creating a second signature based on a second function, where an input to the second function is the first signature. In one example, the second function is a multiplicative inverse function and the method further includes creating the second signature that is a multiplicative inverse value of the first signature with respect to a first irreducible polynomial. The method additionally includes creating a chain of signatures, where each of the signatures is a multiplicative inverse value of a previous output with respect to a respective irreducible polynomial.

Disclosed are a calculation device for encryption using a public key and an encryption method thereof. The present method comprises: a step for setting a secret key, and generating a public key using the secret key and an error extracted from a discrete Gaussian distribution or a distribution that is within a short statistical distance thereto; and a step for applying the public key to a message, and then performing a rounding process to encrypt the message. Accordingly, encryption efficiency can be enhanced.

Zero round trip secure communications are implemented based on noisy secrets with a polynomial secret sharing scheme. A sender identifies two negotiated noisy secrets associated with an encrypted message to send to a receiver system. The sender utilizes a first negotiated noisy secret for sub-key selection, and generates a secret polynomial using Shamir's polynomial-based secret sharing scheme with N positive integer points and a message key as a secret. The sender divides the first negotiated noisy secret into a plurality of sub-keys, and divides a second negotiated noisy secret into test blocks of a length equivalent to a length of a sub-key. The sender utilizes each of the plurality sub-keys for encrypting a corresponding test block along with one unique point of the secret polynomial. Moreover, the sender sends all encrypted test blocks and corresponding encrypted points of the secret polynomial to the receiver with the encrypted message.

Cryptographic methods and systems for key exchange, digital signature and zero-knowledge proof. In the digital signature scenario, there is provided a method of signing a digital document, comprising: obtaining a private cryptographic key associated with the signer; obtaining a digital asset from the digital document; selecting a base data element; computing a plurality of signature data elements from (i) the digital asset, (ii) the base data element and (iii) the private cryptographic key; and transmitting the digital document and the plurality of signature data elements to a recipient over a data network. Provenance of the digital document is confirmable by the recipient carrying out a predefined computation involving the digital document, the signature data elements, a plurality of noise variables and a public cryptographic key corresponding to the private cryptographic key associated with the signer. In the zero-knowledge proof scenario, the digital asset plays the role of a challenge data element.

Embodiments of the invention relate to symmetric encryption that converts plain text to Diophantine equations, i.e. cipher text, and creates a symmetric key which is held by a sender (or encryption apparatus) and a recipient (or decryption apparatus). The key is used by the decryption apparatus to decrypt the Diophantine equations, and convert them to original plain text. Particularly, undecidable encryption and artificial intelligence (AI) are employed in combination. More particularly, the AI would exclude any class of Diophantine equations which has been solved or deciphered without key, or known to be solvable. In the event certain classes of Diophantine equations are solved in the future, the AI will exclude the use of these solved or solvable classes of Diophantine equation in encryption.

A method of securely accessing a database with sensitive data, such as the clinical information of patients, by a client in a privacy-preserving manner, including: communicating with the server to obtain tags for specific attribute-value pairs when the client is authorized to make a query; imposing a tag quota per client and restricting tag generation to authorized query terms with valid digital signatures from a third-party authority; storing the tags and their associated query terms in confidence for future queries; sending a combination of tags that define the terms of a conjunctive query over a secure channel to a proxy; receiving from the proxy encrypted coefficients of a polynomial whose roots are indices to the query results; decrypting the encrypted coefficients in a first protocol with the server; calculating the roots of the polynomial based upon the decrypted coefficients and discarding any superfluous roots; obtaining the encrypted records associated with the calculated roots from the proxy; and decrypting the encrypted records in a second protocol with the server.

Disclosed is a method and apparatus for modulus refresh, where the method for modulus refresh of a ciphertext in homomorphic encryption includes receiving a first ciphertext corresponding to a first modulus, generating a second ciphertext by performing a blind rotation on the first ciphertext, and generating a target ciphertext corresponding to a second modulus greater than the first modulus based on the first ciphertext and the second ciphertext.

Provided is a method for generating a fully homomorphic code, which includes: generating an Idempotent polynomial; and generating a fully homomorphic code message by using the generated Idempotent polynomial and a message.