A computer-implemented method for detecting and disabling replay attacks, the method comprising: receiving a transaction to be completed in a blockchain; determining a first memory section of a memory as being a current working section storing transaction information that is designated for use in identifying past transactions already processed, the memory also comprising a second memory section being used as a backup section, wherein the first memory section and the second memory section provide an alternating memory section storage scheme for the transaction information and are alternately used for identifying past transactions already processed, wherein, in normal operation, only one of the first memory section and second memory section serves as the current working section used for identifying past transactions already processed and storing transaction information for received transactions that are determined not to have previously been processed; determining, using a Bloom filter, a probability that the transaction has previously been processed; after determining, using the Bloom filter, the probability that the transaction has previously been processed, determining, from the current working section, whether the transaction has previously been processed; when it is determined that the transaction has previously been processed, bypassing the transaction; when it is determined that the transaction has not previously been processed: processing the transaction; and writing transaction information for the transaction into the current working section; and determining whether a threshold condition is met for initiating a switch-over between the current working section and the backup section after which the second memory section ceases to be the backup section and becomes the current working section and the first memory section ceases to be the current working section and becomes the backup section; wherein the threshold condition is an indication that a misjudgment rate of the current working section is greater than a pre-determined rate, wherein the misjudgment rate corresponds to a misjudgment rate of the Bloom filter. receiving a transaction to be completed in a blockchain; determining a first memory section of a memory as being a current working section storing transaction information that is designated for use in identifying past transactions already processed, the memory also comprising a second memory section being used as a backup section, wherein the first memory section and the second memory section provide an alternating memory section storage scheme for the transaction information and are alternately used for identifying past transactions already processed, wherein, in normal operation, only one of the first memory section and second memory section serves as the current working section used for identifying past transactions already processed and storing transaction information for received transactions that are determined not to have previously been processed; determining, using a Bloom filter, a probability that the transaction has previously been processed; after determining, using the Bloom filter, the probability that the transaction has previously been processed, determining, from the current working section, whether the transaction has previously been processed; when it is determined that the transaction has previously been processed, bypassing the transaction; when it is determined that the transaction has not previously been processed: processing the transaction; and writing transaction information for the transaction into the current working section; and processing the transaction; and writing transaction information for the transaction into the current working section; and determining whether a threshold condition is met for initiating a switch-over between the current working section and the backup section after which the second memory section ceases to be the backup section and becomes the current working section and the first memory section ceases to be the current working section and becomes the backup section; wherein the threshold condition is an indication that a misjudgment rate of the current working section is greater than a pre-determined rate, wherein the misjudgment rate corresponds to a misjudgment rate of the Bloom filter.