Abstract: A method of encrypting data comprises determining, at a first node associated with a first public-private key pair of a cryptography system having a first private key (VA) and a first public key (PA), a common secret (S1) common with the first node and a second node, wherein the second node is associated with a second public-private key pair of the cryptography system having a second private key (VB) and a second public key (PB). The common secret is determined on the basis of the first private key and the second public key, and the properties of the cryptography system are such that the common secret can be determined on the basis of the second private key and the first public key. An encryption key, based on the common secret, is determined for encryption of data (M), and the data is encrypted on the basis of the encryption key.

Abstract: A computer-implemented method of facilitating payments between multiple first parties and a second party, comprising: executing a respective payment channel between each respective first party and an intermediate party by: obtaining a channel opening transaction comprising an output locking a maximum value; obtaining one or more channel closing transactions including a final channel closing transaction, the final channel closing transaction comprising a first output and a second output, the first output locking a first amount of the maximum value, and second output locking a second amount of the maximum value; and generating a payment transaction, wherein the payment transaction comprises a plurality of inputs, each input referencing a second output of a final channel closing transaction, and an output locked to a public key of the second party, the output locking a value based on a total of the second amounts locked by the second outputs.

Abstract: A method performed by a first party, the method comprising: receiving, from a second party, information of a first blockchain transaction, the first blockchain transaction comprising an input and an output, wherein the input of the first blockchain transaction comprises a signature of the second party and wherein the output of the first blockchain transaction is locked to a public key of the first party; performing an action comprising at least one of: receiving authorisation of access to a product or service; issuing authorisation of access to a product or service; providing a product or service; receiving a product or service; in response to performing the action, providing, as part of a first input of a second blockchain transaction, a signature of the first party to unlock the output of the first blockchain transaction

Abstract: A method for enabling a verifying party to verify an identity of a target party or device. The method comprises, in a set-up phase: storing, in a data store, a respective piece of response data for each of a set of one or more responses resulting from a setting-up party inputting a respective set of one or more challenges into a PUF module comprising a physically unclonable function, PUF, to generate the one or more responses based on the PUF; and storing an indication of the set of challenges in the data store. The indication does not comprise a value of each of the challenges in the set, but rather a master challenge from which the set of challenges is derivable by applying a derivation function to the master challenge.

Abstract: A computer-implemented method for secure communication between a set of nodes, wherein a sequence of security levels is defined, wherein a first security level in the sequence is defined as being a most secure level and a final security level in the sequence is defined as being a least secure level, and wherein a respective security of respective security levels in the sequence is defined as decreasing from the first security level to the final security level, wherein each respective node has a respective security certificate associated with a respective security level, wherein each node is configured to communicate with other nodes according to a communication protocol, wherein the method is performed by a first node having a first certificate communicating with a second node having a second certificate according to the communication protocol.

Abstract: The invention provides a computer-implemented method for performing an exchange via a blockchain, comprising the step of submitting a funding transaction to the blockchain network, wherein the funding transaction i) comprises a tokenised contract relating to an asset to be transferred from a second user to a first user; and ii) is signed by the first user. It also comprises the step of sending, from the first user to the second user, one or more subsequent transactions wherein each said subsequent transaction spends an output of the funding transaction and is signed by the first user. It includes the step of submitting one of the subsequent transactions to the blockchain network, the submitted transaction having been signed by the second user.

Abstract: A computer implemented method of using a blockchain to coordinate data transfer over a P2P network. The method comprises obtaining a second hash value, wherein the second hash value is generated by hashing at least a data request with a first hash function to generate a first hash value and then hashing at least the first hash value with a second hash function to obtain the second hash value. The data request is associated with the target data item. A primary request transaction is submitted to a blockchain network, wherein the primary request transaction comprises the second hash value and one or more first outputs, each first output being locked to a respective public key associated with a respective P2P node connected to the requesting P2P node. The target data item is obtained from the target P2P node.

Abstract: A method of generating a blockchain transaction comprising: generating a transaction comprising a locking script comprising a first shared hash value (HV) generated by applying a hash function (HF) to a second shared HV, wherein the second shared HV is generated by applying a HF to a combination of the respective public keys, and wherein the locking script is configured to require an unlocking script to comprise a target public key, a target signature, and an intermediate HV generated based on all but one of the respective public keys, apply the HF to the target public key to generate a target HV, combine the target HV and the intermediate HV to generate a target second shared HV, apply the HF to the target second shared HV to generate a target first shared HV, an verify that the target first HV matches the first shared HV, and verify the target signature.

Abstract: The invention provides a secure method for exchanging entities via a blockchain. The invention incorporates tokenisation techniques, and also techniques for embedding metadata in a redeem script of a blockchain transaction.

Abstract: A computer-implemented method of using a multi-level (ML) data chain protocol to embed a data chain on a core blockchain, comprising: obtaining one or more ML transactions, wherein each ML transaction comprises one or more carrier pairs, each carrier pair comprising an input and an output, wherein each output comprises data associated with the data chain, and wherein each input comprises a signature that signs the carrier pair; generating a first ML block of the ML data chain, wherein the first ML block is a core blockchain transaction and comprises the respective carrier pairs of the obtained one or more ML transactions, wherein for each carrier pair, a respective position index of the respective input corresponds to a respective position index of the respective output, and a first chain output that is for being spent by a respective chain input of a subsequent ML block.

Abstract: A method of communicating a secret between a sender and a recipient is disclosed. The method comprises sending information identifying secrets selectable by the recipient and receiving a first public key of an elliptic curve cryptography system, corresponding to a first secret selected for access by the recipient and for which a first private key is accessible to the recipient. A second public key is received, corresponding to a second secret not selected for access by the recipient, wherein a corresponding second private key is not available to the recipient. First and second secrets encrypted by means of the respective first and second public keys are sent to the recipient, wherein the first secret is accessible to the recipient by means of the first private key, the second secret is inaccessible to the recipient, and the sender is unable to distinguish between the first and second secrets.

Abstract: A method performed by a node of a blockchain network, comprising: accessing the locking script from a first transaction on the blockchain; receiving a second transaction not yet on-chain, the second transaction comprising an unlocking script; extracting from the first transaction or another transaction on the blockchain, a portion of code formulated in a second language other than a first language used for the locking and unlocking scripts; running the extracted portion of code in the second language, wherein as a result thereof the code generates at least one value; writing this value to a storage location readable by the locking script; and running the locking script together with the unlocking script in order to validate the second transaction, wherein the unlocking script is configured to read the first value from said storage location, and a condition for validation according to the locking script is dependent on the first value.

Abstract: A solution for controlling access to a resource such as a digital wallet implemented using a blockchain. Use of the invention during set-up of the wallet can enable subsequent operations to be handled in a secure manner over an insecure channel. An example method comprises splitting a verification element into multiple shares; determining a common secret at multiple nodes in a network; and using the common secret to transmit a share of the verification element between nodes. The shares can be split such that no share is sufficient to determine the verification element and can be stored at separate locations. Upon share unavailability, the share can be retrieved a location accessibility. For safe transmission of the share(s), the common secret is generated at two different nodes independently and used to generate an encryption key for encrypting at least one share of the verification element to be transmitted securely.

Abstract: A computer-implemented method for connecting to a layered network. The layered network comprises a plurality of nodes arranged in an ordered set of layers. The ordered set of layers comprises, in order, a core layer comprising a set of core nodes, a second layer comprising a set of second nodes, and one or more outer layers each comprising a respective set of outer nodes. Each core node is connected to at least one other core node. The method is performed by a connecting node and comprises connecting to the network according to a connection protocol. The connection protocol requires that each node must connect to at least one node of a preceding layer, and each outer node must also connect to at least one core node.

Abstract: A computer-implemented method of using blockchain transactions to issue one or more single-uses tokens for use by one or more respective token redeemers, wherein the method is performed by a token issuer and comprises: generating a token transaction, wherein the token transaction comprises: one or more token outputs, wherein each token output comprises token data representing a respective single-use token, wherein each single-use token is associated with a respective spendable output of the token transaction, and wherein a respective validity of each single-use token is conditional on the respective spendable output being present in an unspent transaction output set of a blockchain; and one or more inputs, wherein at least a first one of the inputs comprises a signature linked to a first public key of the token issuer; and transmitting the token transaction to one or more nodes of a blockchain network to be recorded in the blockchain.

Abstract: A computer implemented method of facilitating a consumption tax on a purchase of one or more goods and/or services by a buyer from a seller, wherein at least the buyer is a buyer-seller who makes an onward sale based on said goods and/or services. The method comprises, by the seller of the purchase, obtaining a first blockchain transaction that can be redeemed by a second blockchain transaction meeting either of two alternative conditions: a first condition requiring at least that the second blockchain transaction is signed with a cryptographic signature of the buyer, and a second condition requiring at least that the second blockchain transaction is signed with at least a cryptographic signature of a tax authority; and in response to receiving a payment of the consumption tax from the buyer, sending the first blockchain transaction to be recorded on a blockchain.

Abstract: A method of encrypting data is disclosed. The method comprises determining, at a first node associated with a first public-private key pair of a cryptography system having a first private key (VA) and a first public key (PA), a common secret (S1) common with the first node and a second node, wherein the second node is associated with a second public-private key pair of the cryptography system having a second private key (VB) and a second public key (PB). The common secret is determined on the basis of the first private key and the second public key, and the properties of the cryptography system are such that the common secret can be determined on the basis of the second private key and the first public key. An encryption key, based on the common secret, is determined for encryption of data (M), and the data is encrypted on the basis of the encryption key, wherein the step of encrypting data includes an exclusive or (XOR) operation.

Abstract: The disclosure relates to a technique for implementing, controlling and automating a task or process on a blockchain. The disclosure is particularly suited for, but not limited to, automated execution of contracts such as smart contracts for financial agreements. However, other types of tasks and non-financial contracts can be implemented. The disclosure can be viewed as the implementation or incarnation of a state machine or DFA on a blockchain by using the unspent outputs of blockchain Transactions to represent the states of the machine, and spending of those outputs as the transition of the machine from one state to another. The disclosure provides a technical realization and implementation of a mathematical model of computation conceived as an abstract machine that can be in one of a finite set of states and can change from one state to another (transition) when a triggering event of a finite set (called input) occurs.

Abstract: A computer-implemented method to participate in a token transfer process for transferring a first quantity of token from a sender node to a recipient node using a blockchain is disclosed. The token transfer process includes a plurality of participating nodes and execution of a set of indirect token transactions between multiple pairs of the participating nodes. The method is implemented at a participating node that performs steps of: obtaining a subset of the set of indirect token transactions including only those transactions for which the participating node is either an input node or an output node; for each indirect token transaction in the subset, collaborating with a respective second participating node included in the indirect token transaction to generate a commitment channel between the participating node and the second participating node; and collaborating with all other participating nodes in executing the indirect token transactions using the generated commitment channels.

Abstract: A computer-implemented method of generating a second transaction for a blockchain. The blockchain comprises a first transaction comprising a first token and a first output transferring an amount of a digital asset between a second party and a first party. The first token represents a first amount of a token asset other than the digital asset, the second transaction is for transferring a second token representing a second amount of the token asset from a first party to a third party. The method is performed by the first party and comprises generating the second transaction. The second transaction comprises a first input configured to unlock the first output of the first transaction, and a first output comprising the second token. The second token comprises data representing the second amount of the token asset, the second amount being less than the first amount.