EP-4742586-A1 - QUANTUM RESISTANT DIGITAL SIGNATURE CRYPTOGRAPHY

EP4742586A1EP 4742586 A1EP4742586 A1EP 4742586A1EP-4742586-A1

Abstract

Computer-implemented methods and systems are provided for securing digital signatures on a computational network to protect against unauthorised access, for example, by a quantum computer or similar system.

Inventors

BERIC, JOHN
Colnot, Cédric
GARRETT, DUNCAN
WARD, MICHAEL

Assignees

Mastercard International Incorporated

Dates

Publication Date: 20260513
Application Date: 20241107

Claims (15)

A computer-implemented method for securing digital signatures on a computational network, comprising: generating, by a first computing device, a digital signature using a private key of an asymmetric cryptographic key pair associated with the first computing device; encrypting, by the first computing device, the digital signature using a secret symmetric encryption key to produce an encrypted digital signature; and sending the encrypted digital signature, by the first computing device, to a second computing device, on a computational network; wherein a public key of the asymmetric cryptographic key pair associated with the first computing device is available at the first computing device and the second computing device, encrypted using the secret symmetric encryption key; and wherein the secret symmetric encryption key is available at the first computing device and the second computing device, based on a secure data transfer.
The computer-implemented method according to claim 1, wherein the encrypting the digital signature using a secret symmetric encryption key to produce an encrypted digital signature comprises: extracting a selection of bytes of the digital signature; encrypting the selection of bytes of the digital signature, using the secret symmetric encryption key, to produce an encrypted selection of the digital signature; and combining the encrypted selection of the digital signature with the digital signature to produce the encrypted digital signature.
The computer-implemented method according to claim 2, wherein the combining the encrypted selection of the digital signature with the digital signature to produce the encrypted digital signature comprises: replacing the selection of bytes of the digital signature with the encrypted selection of the digital signature.
The computer-implemented method according to claim 2, wherein the combining the encrypted selection of the digital signature with the digital signature to produce the encrypted digital signature comprises: replacing an auxiliary selection of bytes of the digital signature with the result of: an XOR function of the encrypted selection of the digital signature and the auxiliary selection of bytes of the digital signature. wherein the selection of bytes and the auxiliary selection of bytes have the same number of bytes, and wherein the selection of bytes and the auxiliary selection of bytes do not overlap.
The computer-implemented method according to any previous claim, wherein the public key of the asymmetric cryptographic key pair associated with the first computing device being available at the first computing device and the second computing device, based on a secure data transfer using the secret symmetric encryption key, comprises the steps of: generating, by the first computing device, the private key and the public key of the asymmetric cryptographic key pair associated with the first computing device; encrypting, by the first computing device, using the secret symmetric encryption key, the public key of the asymmetric cryptographic key pair associated with the first computing device, to produce an encrypted public key; and sending the encrypted public key, by the first computing device, to the second computing device, on the computational network.
A computer-implemented method for securing digital signatures on a computational network, comprising: receiving an encrypted digital signature, at a second computing device, from a first computing device over a computational network; decrypting, by the second computing device, the encrypted digital signature using a secret symmetric encryption key to produce a digital signature; and verifying, by the second computing device, that the digital signature was generated at the first computing device, by using a public key of an asymmetric cryptographic key pair associated with the first computing device; wherein the public key of the asymmetric cryptographic key pair associated with the first computing device is available at the first computing device and the second computing device, encrypted using the secret symmetric encryption key; and wherein the secret symmetric encryption key is available at the first computing device and the second computing device, based on a secure data transfer.
The computer-implemented method according to claim 6, wherein the decrypting the encrypted digital signature using a secret symmetric encryption key to produce a digital signature comprises: extracting an encrypted selection of the digital signature; decrypting the encrypted selection of the digital signature, using the secret symmetric encryption key, to produce a selection of bytes of the digital signature; and replacing the encrypted selection of the digital signature with the selection of bytes of the digital signature to produce the digital signature.
The computer-implemented method according to claim 7, wherein the extracting an encrypted selection of the digital signature comprises: extracting a predetermined selection of the encrypted digital signature to produce the encrypted selection of the digital signature.
The computer-implemented method according to claim 7, wherein the extracting an encrypted selection of the digital signature comprises: extracting a predetermined selection of the encrypted digital signature; and executing an XOR function of the predetermined selection of the encrypted digital signature and an auxiliary predetermined selection of the encrypted digital signature to produce the encrypted selection of the digital signature. wherein the predetermined selection of the encrypted digital signature and auxiliary predetermined selection of the encrypted digital signature have the same number of bytes, and wherein the predetermined selection of the encrypted digital signature and auxiliary predetermined selection of the encrypted digital signature do not overlap.
The computer-implemented method according to any one of claims 6 to 9, wherein the public key of the asymmetric cryptographic key pair associated with the first computing device being available at the first computing device and the second computing device, based on a secure data transfer using the secret symmetric encryption key, comprises the steps of: receiving the encrypted public key, by the second computing device, from the first computing device, over the computational network; and decrypting, by the second computing device, using the secret symmetric encryption key, the encrypted public key, to produce the public key of the asymmetric cryptographic key pair associated with the first computing device.
A first computing device, wherein the first computing device comprises one or more processors and a memory, wherein the memory is coupled to the one or more processors, the memory is configured to store computer program code, the computer program code comprises computer instructions, and the one or more processors invoke the computer instructions, to enable the first computing device to perform the method according to any one of claims 1 to 5.
A second computing device, wherein the second computing device comprises one or more processors and a memory, wherein the memory is coupled to the one or more processors, the memory is configured to store computer program code, the computer program code comprises computer instructions, and the one or more processors invoke the computer instructions, to enable the second computing device to perform the method according to any one of claims 6 to 10.
A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method of any of claims 1 to 10.
A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of any of claims 1 to 10.
A transaction network comprising a first computing device and a second computing device; wherein the first computing device is configured to: generate a digital signature using a private key of an asymmetric cryptographic key pair associated with the first computing device; encrypting the digital signature using a secret symmetric encryption key to produce an encrypted digital signature; and send the encrypted digital signature to the second computing device on a computational network; wherein the second computing device is configured to: receive the encrypted digital signature from the first computing device over the computational network; decrypt the encrypted digital signature using a secret symmetric encryption key to produce a digital signature; and verify that the digital signature was generated at the first computing device, by using a public key of an asymmetric cryptographic key pair associated with the first computing device; wherein the public key of the asymmetric cryptographic key pair associated with the first computing device is available at the first computing device and the second computing device, encrypted using the secret symmetric encryption key; and wherein the secret symmetric encryption key is available at the first computing device and the second computing device, based on a secure data transfer.

Description

FIELD OF THE INVENTION Computer-implemented methods and systems are provided for securing digital signatures on a computational network to protect against unauthorised access, for example, by a quantum computer or similar system. BACKGROUND In traditional asymmetric or public-key cryptographic signatures (e.g., using RSA (Rivest-Shamir-Adleman) or ECC (Elliptic-curve cryptography), and DSA (Digital Signature Algorithm)), data items, such as a public key and a signature signed by a corresponding private key, are made available to the public (or to all of a network). The public may include malicious parties that may wish to compromise data exchange. Security of encrypted data or cryptographic signatures relies on a very high difficulty and/or very high level of computation required to solve intractable mathematical problems associated with the encryption method. Solving said intractable mathematical problems, starting from publicly available data, would be a means of gaining unauthorised access to the data which has been encrypted. Methods, which in classical computing systems suffer from the aforementioned very high difficulty and/or very high level of computation, include cryptographic attacks, such as a brute-force key search attack. However, quantum computers threaten this security by providing a potential means for substantially increasing the feasibility of cryptographic attacks such as a brute-force key search attacks. Quantum computers may therefore be able to recover a private key of an asymmetric key pair, or the data which has been encrypted, based just on the publicly available public key, signature, or encrypted data. This may be achieved within a much shorter and more feasible time frame that is useful to a malicious party. A number of quantum resistant algorithms have been proposed as an alternative to traditional encryption algorithms, however, these algorithms are, in the main, bloated and inefficient. Further, large quantities of network infrastructure rely on the traditional algorithms, and, as such, a full scale conversion to new quantum resistant algorithms would prove very disruptive and resource intensive. As such, there is a need for a less resource-intensive and less disruptive means for reducing the risk posed by quantum computers to asymmetric encryption based systems, which can be straightforwardly implemented. SUMMARY OF INVENTION A first aspect of the invention herein provides a computer-implemented method for securing digital signatures on a computational network, including: generating, by a first computing device, a digital signature using a private key of an asymmetric cryptographic key pair associated with the first computing device; encrypting, by the first computing device, the digital signature using a secret symmetric encryption key to produce an encrypted digital signature; and sending the encrypted digital signature, by the first computing device, to a second computing device, on a computational network; wherein a public key of the asymmetric cryptographic key pair associated with the first computing device is available at the first computing device and the second computing device, based on a secure data transfer using the secret symmetric encryption key; and wherein the secret symmetric encryption key is available at the first computing device and the second computing device, based on a secure data transfer comprising at least one of a secure data transfer means and a secure channel. Advantageously, this aspect may provide a method for reducing the risk posed by quantum computers to asymmetric cryptography systems that may be straightforwardly retrofitted to such systems. Additionally, the method is less resource-intensive than comparable quantum resistant algorithms. In particular, the step of encrypting the digital signature using a secret symmetric encryption key to produce an encrypted digital signature may provide such a reduction of risk, since symmetric encryption is based on different principles to asymmetric encryption, wherein, unlike asymmetric encryption, the security of symmetric encryption may not be derived from the difficulty or intractability of solving certain mathematical problems solvable by a quantum computer, but rather on the infeasibility of correctly reversing a number of different operations such as substitutions and permutations. Preferably, the network is a closed network or a partially closed network, such as a transaction network. Advantageously, the present invention may be particularly suited to closed or partially-closed networks, as it may be particularly feasible to make the secret symmetric encryption key available at the first computing device and the second computing device, for example, by means of a secure data channel or other secure data transfer means, such as physically moving a (possibly encrypted) data storage device between computing devices on the network. In some embodiments, the encrypting the digital signature using a