Abstract: A computer-implemented method of testing whether or not a blockchain transaction is a double spend attempt, the method being performed by a first party and comprising: generating a first blockchain transaction, wherein the first blockchain transaction comprises an input for unlocking an output of a blockchain transaction previously transmitted to one or more nodes of a blockchain network for inclusion in the blockchain; generating a signature based on the first blockchain transaction and one or more time indicators, each time indicator indicating when the first blockchain transaction was generated and/or transmitted to a second party; and transmitting to the second party, the first blockchain transaction, the signature and the one or more time indicators, wherein at least the first blockchain transaction is transmitted to the second party via an off-chain communication channel.

Abstract: A first blockchain transaction is generated where the first blockchain transaction comprises a redeem script, which comprises a cryptographic public key associated with an initiating party and metadata which includes a hash of an exchange-related document, a redeem address, and an amount of digital currency. A second blockchain transaction to spend the digital currency to the redeem address is generated. A response associated with a responding party and comprising a reference to the exchange-related document is generated. The response is stored in a computer-based repository. A further blockchain transaction is generated, the further blockchain transaction comprising a redeem script, which comprises a cryptographic public key associated with the responding party and metadata which includes a hash of the response and a reference to its location in the repository, and an amount of digital currency.

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: Techniques described herein may be utilized to implement methods and systems for lossless compression and serialization of arithmetic circuits to a bit stream using compression techniques such as the arithmetic coding. An arithmetic circuit representing a smart contract may be compressed using arithmetic coding, thereby generating a compressed arithmetic circuit that can be stored or broadcast to a blockchain network using less computational resources (e.g., data storage resources) than would otherwise be needed to store the arithmetic circuit. The arithmetic circuit can be efficiently compressed using entropy coding based on the frequency of elements in the data structure, such as the arithmetic operator types. Instructions for de-serialization and de-compression can also be embedded in the bit stream, and can be used (e.g., by another computer system) to reconstruct the original circuit in a lossless manner.

Abstract: Techniques described herein may be utilized to serialise and de-serialise arithmetic circuits that are utilized in the execution of computer programs. The arithmetic circuit may be utilized to build a Quadratic Arithmetic Problem (QAP) that is compiled into a set of cryptographic routines for a client and a prover. The client and prover may utilize a protocol to delegate execution of a program to the prover in a manner that allows the client to efficiently verify the prover correctly executed the program. The arithmetic circuit may comprise a set of symbols (e.g., arithmetic gates and values) that is compressed to produce a serialised circuit comprising a set of codes, wherein the set of symbols is derivable from the set of codes in a lossless manner. Serialisation and de-serialisation techniques may be utilized by nodes of a blockchain network.

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 method of encrypting data at an electronic device where the electronic device is associated with a key device. Each device is associated with an asymmetric cryptography pair, each pair including a first private key and a first public key. Respective second private and public keys may be determined based on the first private key, first public key and a deterministic key. A secret may be determined based on the second private and public keys. The data at the electronic device may be encrypted using the determined secret or an encryption key that is based on the secret. Information indicative of the deterministic key may be sent to the key device where the information may be stored.

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 method of sharing a first common secret among a plurality of nodes for enabling secure communication for blockchain transactions. The method comprises determining, for at least one first node a plurality of second common secrets, wherein each second common secret is common to the first node and a respective second node, is determined at the first node based on a first private key of the first node and a first public key of the second node and is determined at the second node based on the first private key of the second node and the first public key of the first node. The method further comprises exchanging encrypted shares of the first common secret among the plurality of nodes to enable each of the plurality of nodes to reach a threshold number of shares of the first common secret to access the first common secret.

Abstract: The computer-implemented invention provides a method and corresponding system for controlling access to and/or use of an internet-enabled resource. The invention uses an electronic ledger such as, for example, the Bitcoin blockchain. The resource may be an IoT device or system. Access to the resource is permitted or enabled upon provision of a cryptographic key e.g., a private key which corresponds to a public key which has been stored in memory. In one embodiment, the public key is stored in a DHT. Access to the resource is prevented or disabled by removing the public key from memory and using a redeem script of a second blockchain Transaction to spend a tokenised output of a first blockchain Transaction. The second transaction detokenizes the token (or ‘coloured coin’) contained within the first Transaction. In order to prevent further access to the resource, an encrypted message is sent to the internet-enabled resource, wherein the message communicates a public key and the redeem script.

Abstract: A specialized network (“merchant”) node to facilitate fast distribution of blockchain transactions over a network of interconnected nodes, as subset of which are merchant nodes interconnected by an overlay network. The merchant node includes a memory storing an assigned portion of a distributed mempool structured as a distributed hash table, the distributed mempool containing pending transactions awaiting confirmation. The merchant node operates by receiving a transaction, including a transaction identifier; hashing the new transaction identifier to obtain a key; determining, using the key, whether the transaction is stored in the distributed mempool or not and, if not, then storing the transaction in the distributed mempool as a pending transaction; and sending the transaction to a set of nodes other than merchant nodes using peer-to-peer connections. The invention may be used in conjunction with the Bitcoin blockchain or an alternative.

Abstract: According to one perspective, the invention provides a technical arrangement to calculate, register and/or apportion costs and/or generate income in proportion to the current ownership of an asset. One or more embodiments also comprise a novel technique for generating cryptographic sub-keys. Thus, one benefit provided by the invention is that it allows the secure distribution of costs and income for an asset registered and maintained on the Blockchain. In turn, this increases the capability of such assets to meet the real-world needs of various entities such as the asset itself and investing parties.

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: The disclosure relates to a blockchain-implemented system and method of controlling the transmission and/or distribution of digital content. A first user transfers a deposit quantity of cryptocurrency to a common address. A first node associated with the first user: sends a request to the second node to provide an episode of digital content from a series of digital content; determines a payment transaction to transfer a payment quantity of cryptocurrency to the second user based on a quantity of episodes of digital content in the series; and signs and sends the payment transaction to a second node. The second node associated with the second user: receives the request and the payment transaction; verifies the payment transaction; and based on a result of verifying: provides access to the episode of digital content to the first node; and co-signs and sends the payment transaction to a distributed ledger.

Abstract: A computer-implemented method for adapting connections between nodes of 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 an adapting node, the adapting node being a node of the layered network that is connected to one or more second nodes and multiple core nodes. The method comprises, based on one or more network properties of the layered network, disabling a respective connection between the adapting node and at least one but not all of the multiple core nodes.

Abstract: A method (300) and system (1) of determining a common secret for two nodes (3, 7). Each node (3, 7) has a respective asymmetric cryptography pair, each pair including a master private key and a master public key. Respective second private and public keys may be determined based on the master private key, master public key and a deterministic key. A common secret may be determined at each of the nodes based on the second private and public keys. In one example, a node (3, 7) may determine the common secret based on (i) a second private key based on the node's own master private key and the deterministic key; and (ii) a second public key based on the other node's master public key and the deterministic key. The invention may be suited for use with, but not limited to, digital wallets, blockchain (e.g. Bitcoin) technologies and personal device security.

Abstract: A method comprising, at an attesting node of a network: receiving a sequence of data items from one or more client nodes of the network, determining an order of the sequence of data items, and attesting to the order by: including an indication of a respective set of one or more of the data items in each of a series of blockchain transactions. Each successive transaction comprises a respective input pointing to an output of the respective preceding transaction, wherein the output of the respective preceding transaction comprises a locking script, and the input of the respective successive transaction includes an unlocking script comprising a respective signature based on a respective key in a series of keys. The respective signature in each successive transaction signs a portion of the respective successive transaction including at least the indication of the respective set of data items.

Abstract: A method performed in a layered network. The layered network comprises a core layer comprising one or more core nodes, one or more intermediate layers each comprising one or more intermediate layer nodes, and one or more outer layers each comprising one or more outer layer nodes. Each of the core nodes is a node of a blockchain network. One or more intermediate layer nodes are smart contracts nodes providing a smart contract service for maintaining the state of a smart contract. One or more outer layer nodes are client nodes of the smart contract service. The method included, by a smart contract node: recording a state of the smart contract in a record of the state maintained at the first smart contract node. In addition, at least a first transaction also recording the state is recorded on a blockchain of the blockchain network.

Abstract: A method performed in a layered network. The layered network comprises a core layer comprising one or more core nodes, one or more intermediate layers each comprising one or more intermediate layer nodes, and one or more outer layers each comprising one or more outer layer nodes. Each core node is a node of a blockchain network. At least some intermediate layer nodes are database nodes. At least some outer layer nodes are client nodes. Each database node stores at least part of a distributed database. The method includes, at a database node: receiving one or more update requests from one or more client nodes requesting to update a database entry; and for each update request, applying the update locally and/or forwarding to another database node.

Abstract: A computer-implemented method (and corresponding system) is provided, that enables or facilitates the execution of a portion of source code, written in a high-level language (HLL), on a blockchain platform. The method and system can include a blockchain compiler, arranged to convert a portion of high-level source code into a form that can be used with a blockchain platform. This may be the Bitcoin blockchain or an alternative. The method can include: receiving the portion of source code as input; and generating an output script comprising a plurality of op_codes. The op_codes are a subset of op_codes that are native to a functionally-restricted, blockchain scripting language. The outputted script is arranged and/or generated such that, when executed, the script provides, at least in part, the functionality specified in the source code.