Abstract: In some embodiments, a method sends first messages that request first information for a set of blocks of the blockchain to the N replicas. Each replica maintains a respective instance of the blockchain. Second messages is received from at least a portion of the N replicas. The second messages include the first information for the set of blocks from each respective instance of the blockchain that is maintained by the N replicas. The method analyzes the first information to determine whether a consensus on the first information is reached by a number of replicas. When consensus is reached, a request is sent to a replica for one or more blocks to back up to a backup blockchain and second information is received for the one or more blocks from the replica. The method uses the second information to back up the one or more blocks in the backup blockchain.

Abstract: The present disclosure is directed to a novel reconfiguration framework for a BFT SMR system. With this framework, the configuration of both the system itself and the clients of the system can be modified in a live manner (i.e., without taking the system offline) while preserving correct system operation.

Abstract: An asynchronous state machine replication solution in a system of replicas includes executing multiple instances of a consensus protocol, referred to as leader-based views (LBVs) in each replica, where each replica is a leader participant in one of the LBV instances. Each replica drives a decision based on the consensus being reached among the LBV instances, rather than relying the expiration of timers and view changes to drive progress.

Abstract: The present disclosure is directed to a leader-based partially synchronous BFT SMR protocol that improves upon existing protocols by exhibiting two rounds of communication latency, linear authenticator complexity, and optimistic responsiveness. This is achieved through the novel use of an aggregate signature scheme as part of the protocol's view-change procedure.

Abstract: A method and system for performing a flexible Byzantine fault tolerant (BFT) protocol. The method includes sending, from a client device, a proposed value to a plurality of replica devices and receiving, from at least one of the plurality of replica devices, a safe vote on the proposed value. The replica device sends the safe vote, based on a first quorum being reached, to the client device and each of the other replica devices of the plurality of replica devices. The method further includes determining that a number of received safe votes for the proposed value meets or exceeds a second quorum threshold, selecting the proposed value based on the determination, and setting a period of time within which to receive additional votes. The method further includes, based on the period of time elapsing without receiving the additional votes, committing the selected value for the single view.

Abstract: The present disclosure is directed to a leader-based partially synchronous BFT SMR protocol that improves upon existing protocols by exhibiting two rounds of communication latency, linear authenticator complexity, and optimistic responsiveness. This is achieved through the novel use of an aggregate signature scheme as part of the protocol's view-change procedure.

Abstract: A method and system for performing a flexible Byzantine fault tolerant (BFT) protocol. The method includes sending, from a client device, a proposed value to a plurality of replica devices and receiving, from at least one of the plurality of replica devices, a safe vote on the proposed value. The replica device sends the safe vote, based on a first quorum being reached, to the client device and each of the other replica devices of the plurality of replica devices. The method further includes determining that a number of received safe votes for the proposed value meets or exceeds a second quorum threshold, selecting the proposed value based on the determination, and setting a period of time within which to receive additional votes. The method further includes, based on the period of time elapsing without receiving the additional votes, committing the selected value for the single view.

Abstract: In one set of embodiments, a computer system can initialize a counter that is shared by a plurality of software processes, where each software process is programmed to increment the counter a predefined number of times. The computer system can further run the plurality of software processes concurrently. Upon completion of the plurality of software processes, the computer system can apply one or more functions to the shared counter and output the result as an entropy sample.

Abstract: In one set of embodiments, a computer system can allocate a memory buffer in a dynamic random access memory (DRAM), determine a plurality of DRAM rows covered by the memory buffer, and execute a Rowhammer attack against a target row in the plurality of DRAM rows, thereby yielding randomly flipped bits in one or more neighboring DRAM rows. The computer system can then compute a value based on the randomly flipped bits and output the value as an entropy sample.

Abstract: In one set of embodiments, a computer system can initiate a memory stress test on a memory subsystem of the computer system, where the memory subsystem including a dynamic random access memory (DRAM). Then, while the memory stress test is running, the computer system can execute a plurality of access operations for accessing the DRAM, measure the time taken to complete each access operation, combine the measured times to compute a value, and output the value as an entropy sample.

Abstract: In some embodiments, a method receives a share of a signature of a decision block from at least a portion of the plurality of replicas. The share of the signature being generated when a respective replica signs the decision block and the decision block includes a set of requests from a client for a service. A combined signature is created based on the share of the signature block from at least the portion of the plurality of replicas. The method broadcasts a message that includes the combined signature to the plurality of replicas. The plurality of replicas use the combined signature to determine whether to process the decision block for the service.

Abstract: In some embodiments, a method sends first messages that request first information for a set of blocks of the blockchain to the N replicas. Each replica maintains a respective instance of the blockchain. Second messages is received from at least a portion of the N replicas. The second messages include the first information for the set of blocks from each respective instance of the blockchain that is maintained by the N replicas. The method analyzes the first information to determine whether a consensus on the first information is reached by a number of replicas. When consensus is reached, a request is sent to a replica for one or more blocks to back up to a backup blockchain and second information is received for the one or more blocks from the replica. The method uses the second information to back up the one or more blocks in the backup blockchain.

Abstract: In some embodiments, a method receives a share of a signature of a decision block from at least a portion of the plurality of replicas. The share of the signature being generated when a respective replica signs the decision block and the decision block includes a set of requests from a client for a service. A combined signature is created based on the share of the signature block from at least the portion of the plurality of replicas. The method broadcasts a message that includes the combined signature to the plurality of replicas. The plurality of replicas use the combined signature to determine whether to process the decision block for the service.

Abstract: An asynchronous state machine replication solution in a system of replicas includes executing multiple instances of a consensus protocol, referred to as leader-based views (LBVs) in each replica, where each replica is a leader participant in one of the LBV instances. Each replica drives a decision based on the consensus being reached among the LBV instances, rather than relying the expiration of timers and view changes to drive progress.

Abstract: Techniques for implementing linear view-change in a Byzantine Fault Tolerant (BFT) protocol running on a distributed system comprising n replicas are provided. According to one set of embodiments, at a time of performing a view-change from a current view number v to a new view number v+1, a replica in the n replicas corresponding to a new proposer for new view number v+1 can generate a PREPARE message comprising a single COMMIT certificate, where the single COMMIT certificate is the highest COMMIT certificate the new proposer is aware of. The new proposer can then transmit the PREPARE message with the single COMMIT certificate to all other replicas in the n replicas.

Abstract: In some embodiments, a method implements a Byzantine fault tolerant protocol. A first replica detects a condition to cause a view change procedure to move from a current view to a next view. The first replica sends a message indicating the first replica wants to leave the current view. Also, the first replica receives a set of messages from second replicas indicating a respective second replica wants to leave the current view. The first replica determines when a property is received to the leave the current view based on the set of messages from the set of second replicas. When it is determined the property is received, the first replica performs a process to leave the current view. When it is determined the property is not received, the first replica stays in the current view and participating in processing a request from a client in the current view.

Abstract: In some embodiments, a first replica sends a message to second replicas for pre-processing of an operation. The first replica receives pre-processing results from the second replicas. A pre-processing result is generated by pre-processing the operation using a first state. The first replica analyzes the pre-processing results to determine whether an agreement on a validated pre-processing result is received. When it is determined the agreement on the validated pre-processing result is received, the first replica performs a consensus protocol stage with the second replicas to order the request in an order of execution of requests that defines when to execute the request with respect to another request at the second replicas. Information for the validated pre-processing result is provided to the set of second replicas to determine whether contention results between the first state and a second state that is based on the order of execution of requests.

Abstract: In one set of embodiments, each server executing a secure multi-party computation (MPC) protocol can receive shares of inputs to the MPC protocol from a plurality of clients, where each input is private to each client and where each share is generated from its corresponding input using a threshold secret sharing scheme. Each server can then verify whether the shares of the plurality of inputs are valid/invalid and, for each invalid share, determine whether a client that submitted the invalid share or a server that holds the invalid share is corrupted. If the client that submitted the invalid share is corrupted, each server can ignore the input of that corrupted client during a computation phase of the MPC protocol. Alternatively, if the server that holds the invalid share is corrupted, each server can prevent that corrupted server from participating in the computation phase.

Abstract: In some embodiments, a method implements a Byzantine fault tolerant protocol. A first replica detects a condition to cause a view change procedure to move from a current view to a next view. The first replica sends a message indicating the first replica wants to leave the current view. Also, the first replica receives a set of messages from second replicas indicating a respective second replica wants to leave the current view. The first replica determines when a property is received to the leave the current view based on the set of messages from the set of second replicas. When it is determined the property is received, the first replica performs a process to leave the current view. When it is determined the property is not received, the first replica stays in the current view and participating in processing a request from a client in the current view.

Abstract: The present disclosure is directed to a leader-based partially synchronous BFT SMR protocol that improves upon existing protocols by exhibiting two rounds of communication latency, linear authenticator complexity, and optimistic responsiveness. This is achieved through the novel use of an aggregate signature scheme as part of the protocol's view-change procedure.