Certificate based security using post quantum cryptography

Establishing secure communications by sending a server certificate message, the certificate message including a first certificate associated with a first encryption algorithm and a second certificate associated with a second encryption algorithm, the first certificate and second certificate bound to each other, signing a first message associated with client-server communications using a first private key, the first private key associated with the first certificate, signing a second message associated with the client-server communications using a second private key, the second private key associated with the second certificate, the second message including the signed first message, and sending a server certificate verify message, the server certificate verify message comprising the signed first message and the signed second message.

BACKGROUND

The disclosure relates generally to establishing secure network communications. The disclosure relates particularly to communications handshakes utilizing multiple certificates and a combination of encryption algorithms.

The advent of large-scale quantum computing systems raises the possibility that the use of Shor's algorithm and such quantum devices may compromise traditional cryptographic algorithms such as RSA (Rivest-Shamir-Adleman), ECC, (elliptic curve cryptography) or similar techniques. Further, though such a means to compromise traditional cryptographic algorithms is not currently available, the security of current encrypted communications and data storage systems will be at risk once such systems become available. What is needed is a security protocol which will protect communications and data both now and, in the future, once traditional cryptographic methods are no longer sufficient. Legacy communications and data storage protocols must be enhanced to provide this additional protection without disrupting the current protocols.

SUMMARY

Aspects of the invention disclose methods, systems and computer readable media associated with establishing secure communications by sending a server certificate message, the certificate message including a first certificate associated with a first encryption algorithm and a second certificate associated with a second encryption algorithm, the first certificate and second certificate bound to each other, signing a first message associated with client-server communications using a first private key, the first private key associated with the first certificate, signing a second message associated with the client-server communications using a second private key, the second private key associated with the second certificate, the second message including the signed first message, and sending a server certificate verify message, the server certificate verify message comprising the signed first message and the signed second message.

DETAILED DESCRIPTION

In an embodiment, one or more components of the system can employ hardware and/or software to solve problems that are highly technical in nature (e.g., sending and receiving communications protocol messages, verifying entity identities, validating digital certificates, validating digital signature, etc.). These solutions are not abstract and cannot be performed as a set of mental acts by a human due to the processing capabilities needed to facilitate establishing secure client-server communications links, for example. Further, some of the processes performed may be performed by a specialized computer for carrying out defined tasks related to securing communications. For example, a specialized computer can be employed to carry out tasks related to communications security handshake protocols, or the like.

Aspects of the invention disclose methods, systems and computer readable media associated with establishing secure communications by receiving a client hello message from a client device, sending a server hello message, sending a server certificate message, the certificate message including a first certificate associated with a first encryption algorithm and a second certificate associated with a second encryption algorithm, the first certificate and second certificate bound to each other, signing a first message associated with client-server communications using a first private key, the first private key associated with the first certificate, signing a second message associated with the client-server communications using a second private key, the second private key associated with the second certificate, the second message including the signed first message, sending a server certificate verify message, the server certificate verify message comprising the signed first message and the signed second message, receiving. by the one or more server computer processors, a client certificate message in response to the server hello message, the client certificate message comprising a third certificate associated with the first encryption algorithm and a fourth certificate associated with the second encryption algorithm, the third certificate and fourth certificate bound to each other, receiving, by the one or more server computer processors, a client certificate verify message, the client certificate verify message comprising a third message associated with client-server communications signed using a third private key, the third private key associated with the third certificate, and a fourth message associated with the client-server communications signed using a fourth private key, the fourth private key associated with the fourth certificate, the fourth message including the third message, and receiving a client finished message from the client device, and sending a server finished message in response to receiving the client finished message.

Disclosed embodiments provide the benefits of linking two certificates, one based upon traditional cryptographic methods, and one based upon lattice or post quantum cryptographic (PQC) methods in a way that ensures a secure communications link established through the two certificates unless both the PQC and TC methods are broken by a malicious actor.

Traditional cryptographic methods (TC) based upon RSA or ECC are vulnerable to being broken by the use of large-scale quantum computers. RSA and ECC are based upon the use of large prime numbers which are multiplied together yielding a result. A large-scale quantum computer, using Shor's algorithm, should be able to easily defeat an encryption algorithm based upon the use of factors, such as RSA or ECC.

Internet communications between computing entities include an initial “handshake” between the entities. The entities' initial, unencrypted communications occur over the course of the handshake introducing the entities to each other. Through the handshake, the entities exchange unencrypted information necessary to establish the attributes of the ensuing communications between the entities. The attributes include the exchange of information needed to establish the encryption protocol which will be used for encrypting and decrypting data, as well as information necessary for the entities to verify each other's identity including public keys.

Typical communications handshakes, such as a transport level security (TLS) handshake, rely upon public key certificates, such as an x.509 certificate, validated by secure digital signatures based upon RSA, ECC, or a similar traditional factor-based encryption public key infrastructure. A malicious actor may have access to the handshake communications, may break the TC of one of the parties and may then impersonate that party using a falsified private key.

Lattice-based encryption algorithms use public-private key pairs generated using lattice, or array-based mathematics. Such algorithms are thought not susceptible to being broken through the use of a quantum computer. Such algorithms are considered post-quantum cryptographic (PQC) algorithms.

As legacy TLS protocols are based upon the use of TC, simply replacing the TC with PQC may introduce backwards compatibility issues into global internet communications. What is needed is a backwards compatible communication linking protocol which is not susceptible to being broken through the use of a quantum computer. Disclosed methods prevent this by the use of two certificates which are cryptographically bound to each other, a TC, factor-based certificate and a PQC, lattice-based certificate. Each of the two certificates are issued by a certificate authority (CA) trusted by the entities. The malicious actor cannot break the lattice-based encryption with the quantum computer. The hybrid handshake protocol based upon the combination of a TC certificate cryptographically bound to a PQC certificate enables the establishment of communications links between networked entities in a post-quantum world.

In TLS terms, each of the server's certificate and certificate verify messages includes two sets of certificate chains and two sets of verifications data, respectively. The messages are structured as two message each to simplify processing and enable the use of current TLS message processing logic. Disclosed embodiments enable secure communications by requiring that PQC verification data is validated before TC verification data may be validated. PQC must be broken before the TC can be attacked. A malicious actor must break both the PQC and the TC to successfully attack the communications link.

A TLS handshake begins with a client device sending a client hello message to a server. The handshake proceeds with the server responding to the client hello message by sending a server hello message. The exchange of the hello messages includes a negotiation of the encryption protocol to be used and the exchange of client and server generated random numbers to be used in subsequent exchanges of encrypted data. As an example, the client hello message includes the TLS version used by the client, compression methods to be used, cipher suite options supported by the client for the communications, and a random character string to be used for encrypted data exchanges. The client hello message may include one or more extensions such as an encryption extension for encrypting TLS handshake data following the hello messages. The server hello message may include the servers' choice of cipher suites from the provided options, and a different random number for use in encrypting the communications.

The server then sends a TLS certificate message to the client. The TLS certificate message includes two certificate chains embedded in the message, one based on TC and one based on PQC. The two certificate chains may each include a series of certificates, starting with an end-entity certificate of the server, including one or more intermediate certificates and ending with a root certificate. The root certificate is issued and signed by a certificate authority trusted by the entities. In an embodiment, the certificate chains each include a single certificate.

Upon receipt of the server certificate message, the client device decodes the two certificate chains and validates each certificate chain independently. The client ensures that each certificate of each of the two certificate chains has not expired or been revoked, that the domain name of the certificate matches the domain of the server, that the digital signature of each certificate of each chain is valid and that the root certificate of each chain was issued by a CA trusted by the client.

In an embodiment, the client uses the public key of the CA to validate the signature of the server's end-entity certificate. In an embodiment, the client uses the public key from an intermediate certificate to validate the signature of the end entity certificate and uses the public key of the CA root certificate to validate the root certificate signature and the intermediate certificate signature.

For the TC certificate chain, the public keys and digital signatures are based upon a TC public-private key pair. For the PQC certificate chain, the signatures and public keys are based upon a public-private key pair derived using the PQC algorithm.

PQC algorithms include lattice-based encryption methods including CRYSTALS-DILITHIUM, FALCON, RAINBOW, CLASSIC McELIECE, CRYSTALS-KYBER, NTRU, SABER, and other lattice-based algorithms. (Note: the term(s) “CRYSTALS-DILITHIUM”, “FALCON”, “RAINBOW”, “CLASSIC McELIECE”, “CRYSTALS-KYBER”, “NTRU”, and “SABER” may be subject to trademark rights in various jurisdictions throughout the world and are used here only in reference to the products or services properly denominated by the marks to the extent that such trademark rights may exist.)

In an embodiment, the server composes a certificate verify message for the client. The certificate verify message serves to provide proof that the server has possession of the PQC and TC private keys associated with the PQC and TC certificates respectively. The certificate verify message includes two messages. The first message includes the current transcript of the messages exchanged between the client and the server up to this point, signed using the private PQC key of the server. The second message includes the current transcript of the exchanged messages appended by the server with the first message, the appended transcript signed using the TC private key of the server, generating a traditional server certificate verify message. The server combines the first and second certificate verify messages and sends the combination as a single certificate verify message to the client.

The client receives the combined certificate verify messages and separates the two messages. The client has possession of the current messaging transcript and the public PQC key of the server—from the process of validating the PQC certificate of the server. The client uses the current messaging transcript and server PQC public key to verify the PQC digital signature of the PQC certificate verify portion of the server certificate verify message. The client verifies the TC signature of the TC portion of the combined server certificate message using the message transcript including the signed first message contents provided in the PQC portion of the combined server certificate verify message. The client uses the appended messaging transcript and the server's public TC key, obtained during the process of validating the server's TC certificate.

In an embodiment, the method further binds the TC and PQC certificates. The method creates the PQC and TC certificates having the same subject name, issuer name, and subject alternative name. The method sets the constraints of the TC as identical to those of the PQC with the exceptions of the serial number the public keys, and the signatures of the two certificates. In this embodiment, the method sets the serial number or an extension of the TC equal to a hash (SHA1, SHA256, or other hash function) of the PQC certificate data. A binding value set as the output of a hash function cannot be broken using a large-scale quantum computer or a traditional non-quantum computer. In this embodiment, the client validates that the TC serial number or extension when used contains the hash of the PQC certificate data and that all other TC and PQC certificate data attributes match.

In an embodiment, mutual entity verification is desired as indicated by a certificate request message sent from the server to the client. In response to the certificate request message, the client sends a certificate message including each of a client TC and PQC certificate. The client then generates and sends a combined certificate verify message. This includes creating a first certificate verify message by signing the current message transcript with the client's PQC private key, and then appending the first certificate verify message to the current messaging transcript and signing the appended transcript using the client's TC private key.

In an embodiment, the exchange of client and server hello messages does not result in the use of the PQC certificate as the client does not provide support for its use. In this embodiment, the method passes only the TC certificate and TC certificate verify portions of the messages. In this embodiment, the method provides backward compatibility during any time frame where all network entities haven't transitioned to the use of PQC-based protocols.

FIG.1provides a schematic illustration of exemplary network resources associated with practicing the disclosed inventions. The inventions may be practiced in the processors of any of the disclosed elements which process an instruction stream. As shown in the figure, a networked Client device110connects wirelessly to server sub-system102. Client device104connects wirelessly to server sub-system102via network114. Client devices104and110comprise communications security program (not shown) together with sufficient computing resource (processor, memory, network communications hardware) to execute the program. Communications handshakes between client devices104,110and server sub-system102may include the use of disclosed embodiments to enable secure communications between verified entities as well as the exchange of encrypted data. As shown inFIG.1, server sub-system102comprises a server computer150.FIG.1depicts a block diagram of components of server computer150within a networked computer system1000, in accordance with an embodiment of the present invention. It should be appreciated thatFIG.1provides only an illustration of one implementation and does not imply any limitations with regard to the environments in which different embodiments can be implemented. Many modifications to the depicted environment can be made.

Server computer150can include processor(s)154, memory158, persistent storage170, communications unit152, input/output (I/O) interface(s)156and communications fabric140. Communications fabric140provides communications between cache162, memory158, persistent storage170, communications unit152, and input/output (I/O) interface(s)156. Communications fabric140can be implemented with any architecture designed for passing data and/or control information between processors (such as microprocessors, communications and network processors, etc.), system memory, peripheral devices, and any other hardware components within a system. For example, communications fabric140can be implemented with one or more buses.

Memory158and persistent storage170are computer readable storage media. In this embodiment, memory158includes random access memory (RAM)160. In general, memory158can include any suitable volatile or non-volatile computer readable storage media. Cache162is a fast memory that enhances the performance of processor(s)154by holding recently accessed data, and data near recently accessed data, from memory158.

Program instructions and data used to practice embodiments of the present invention, e.g., the communications security program175, are stored in persistent storage170for execution and/or access by one or more of the respective processor(s)154of server computer150via cache162. In this embodiment, persistent storage170includes a magnetic hard disk drive. Alternatively, or in addition to a magnetic hard disk drive, persistent storage170can include a solid-state hard drive, a semiconductor storage device, a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory, or any other computer readable storage media that is capable of storing program instructions or digital information.

The media used by persistent storage170may also be removable. For example, a removable hard drive may be used for persistent storage170. Other examples include optical and magnetic disks, thumb drives, and smart cards that are inserted into a drive for transfer onto another computer readable storage medium that is also part of persistent storage170.

Communications unit152, in these examples, provides for communications with other data processing systems or devices, including resources of client computing devices104, and110. In these examples, communications unit152includes one or more network interface cards. Communications unit152may provide communications through the use of either or both physical and wireless communications links. Software distribution programs, and other programs and data used for implementation of the present invention, may be downloaded to persistent storage170of server computer150through communications unit152.

I/O interface(s)156allows for input and output of data with other devices that may be connected to server computer150. For example, I/O interface(s)156may provide a connection to external device(s)190such as a keyboard, a keypad, a touch screen, a microphone, a digital camera, and/or some other suitable input device. External device(s)190can also include portable computer readable storage media such as, for example, thumb drives, portable optical or magnetic disks, and memory cards. Software and data used to practice embodiments of the present invention, e.g., communications security program175on server computer150, can be stored on such portable computer readable storage media and can be loaded onto persistent storage170via I/O interface(s)156. I/O interface(s)156also connect to a display180.

Display180provides a mechanism to display data to a user and may be, for example, a computer monitor. Display180can also function as a touch screen, such as a display of a tablet computer.

FIG.2provides a flowchart200, illustrating exemplary activities associated with the practice of the disclosure. After program start, at block210, communications security program175of a server receives a client hello message including client information regarding supported TLS protocols, cipher suite options and client generated random number.

At block220, the server sends a server hello message indicating the server's choice of cipher suite from the options provided and including a server generated random number.

At block230, the server sends a server certificate message. The server certificate message includes two certificates or certificate chains. The certificates or certificate chains include a first certificate or certificate chain signed using a first digital signature associated with a first server private key from a PQC algorithm, and a second certificate, or certificate chain signed using a second digital signature associated with a second server private key from a TC encryption algorithm.

At block240, communications security program175of the server signs a first message using the first server PQC private key, the message includes the transcript of the client-server messaging.

At block250, communications security program175of the server signs a second message with the second server TC private key. The second message includes the current client-server messaging transcript appended to include the first message.

At block260, communications security program175of the server combines the first and second messages into a single server certificate verify message and sends the combined messages to the client.

At block270, communications security program175receives a client finished message from the client. The client finished message includes a cryptographic hash of all previous client-server messaging, encrypted using an agreed upon encryption algorithm.

At block280, communications security program175sends a server finished message including a cryptographic hash of all previous client-server messaging traffic from the handshake protocol.

It is understood that the TLS handshake protocol may include additional messages between the client and server relating to the exchange of information necessary to generate an encryption key for the encryption/decryption of data and other purposes.

Schematic300ofFIG.3illustrates messaging traffic between a client310and server320, according to an embodiment of the invention. As shown in the Figure, a client310, sends a client hello message315to the server320. Server320responds by sending a server hello message325, a server certificate message330, and a server certificate verify message340. Each of the server certificate message330, and server certificate verify message340, include two separate messages. Server certificate message330includes a server PQC certificate message332and a server TC certificate message334. Server certificate verify message340includes a first message342signed with a server PQC private key and including the messaging transcript while the second message344includes the messaging transcript appended with the first message and signed using a server TC private key.

FIG.3includes the messages associated with mutual verification including a client certificate message360and client certificate verify message370. Similarly, to the server, client certificate message360includes two messages, a client PQC certificate message362and a client TC certificate message364. Client certificate verify message370also includes two messages, one372including the messaging transcript and signed using the client's PQC private key, the other374including the messaging transcript appended to include the message signed using the client PQC private key, this message signed using the client's TC private key. Item380generally illustrated additional client-server messaging traffic related to the communications handshake between the client and server including client finished and server finished messages.

Characteristics are as follows:

Service Models are as follows:

Deployment Models are as follows:

The present invention may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The invention may be beneficially practiced in any system, single or parallel, which processes an instruction stream. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.