Embodiments implement leakage-free order-preserving encryption by assigning a distinct ciphertext for each plaintext, including repeated plaintext whose ciphertext is randomly inserted. In order to conceal insertion order, the randomized ciphertexts are compressed to minimal ciphertext space. A uniform distribution is achieved by rotating about a modulus on the ciphertexts rather than the plaintexts. The resulting ciphertext distribution has no leakage from the ciphertextseven if an adversary has perfect background knowledge on the distribution of plaintexts. The encryption may be further secured even against passive query monitoring attacks by hiding the access pattern using , -differential privacy, such that the adversary observing a sequence of queries will not learn the frequency of plaintext. The leakage-free order-preserving encryption may be converted into an adjustable encryption scheme to allow querying (e.g., on a remote server).

The present invention relates to methods for a blockchain search system, and particularly, the present invention relates to methods for assuring the data integrity on blockchain hybrid storage. Furthermore, the present invention provides a cost-efficient update scheme to maintain the on-chain index and authenticated data structure and is efficient and scalable under various operational parameters.

A select processor obtains a request to perform a requested operation. The request includes encrypted data and a protected key. The protected key is to be used by the select processor on behalf of an entity unauthorized to use the protected key. The encrypted data is decrypted using the protected key to obtain decrypted data. The requested operation is performed on the decrypted data to obtain resulting data. The resulting data is encrypted (e.g., using the protected key) to obtain encrypted resulting data. The encrypted resulting data is provided to a requester of the request.

An off-chain data storage method and apparatus for supporting the integrity and capacity scalability of a data object stored in an off-chain storage. The off-chain data storage method includes collecting a plurality of transactions for a plurality of data objects, creating a root transaction on the basis of a Merkle root of a Merkle tree created based on the collected transactions, and storing the root transaction in a blockchain storage.

The present invention relates to a method for generating an electronic signature of a document associated with a condensate obtained by a given hash function comprising performing by data-processing means (11b) of a server (10b) of steps of: (a) Receiving said condensate and a zero-knowledge proof of the fact that said condensate is indeed the result of application of said given hash function to said document; (b) Verifying that said zero-knowledge proof is valid; (c) Generating an electronic signature of the document from said condensate.

A computer-implemented method for performing authentication includes: determining, by a database server storing data in a blockchain ledger, a target ledger segment on which time service authentication is to be performed; generating a Merkle tree corresponding to the target ledger segment; determining a root hash of the Merkle tree, the root hash of the Merkle tree being based on a block hash of each data block in a set of one or more data blocks; executing a predetermined time capture process in a trusted execution environment to obtain a trusted time from an interface provided by a trusted time service organization; generating a digital signature for the trusted time and the root hash in the trusted execution environment; and generating a time service certificate including the trusted time, the root hash, and the digital signature.

A method of providing a search index based on a Bloom filter in a distributed data sharing environment based a block chain includes generating, by a data generating device, Bloom filters used as the search index on the basis of a hash value calculated by applying a hash function to a keyword set for searching for data which is to be shared, generating, by a block providing server, a new block on the basis of the Bloom filters and the data received from the data generating device and performing proof of work (PoW) on the new block, for adding the new block to the block chain, and distributing, by a block distributing server, block chain data including the new block added to the block chain.

Computer-implemented methods and systems are provided which are suitable for implementation in transaction validation nodes of a blockchain network. Modified blockchain node structures, network architectures, and protocols for handling large numbers of transactions and large transaction blocks are described. The invention is particularly suited, but not limited, to use with the Bitcoin blockchain. A computer-implemented method is provided which includes: (i) receiving transactions from the blockchain network; (ii) validating transactions received from the blockchain network; (iii) maintaining a distributed, decentralized storage of validated transactions with other transaction validation nodes in the blockchain network; and (iv) distributing data corresponding to said validated transactions to the blockchain network for mining.

A system receives data of one or more types from one or more sources having distinct identities for storing the data in a distributed storage system. The system stores metadata associated with storing the data in data structures in the distributed storage system. The system selects a portion of the data and a portion of the metadata associated with storing the data in the distributed storage system. The system compresses the selected portions of the data and the metadata, encrypts the compressed data and metadata using a single key or using a separate key for each data type, and stores the encrypted compressed data and metadata in the distributed storage system. The system also encrypts unencrypted metadata and associated data during defragmentation procedure.

A method includes: obtaining, by a server storing data in a blockchain ledger, compression point information of the blockchain ledger, in which the compression point information includes identification information of a specified data block, a server digital signature, and a user digital signature, in which the compression point information indicates that a specified portion of the blockchain ledger has passed an integrity verification, and in which the specified portion of the blockchain ledger includes data blocks in the blockchain ledger previous to the specified data block in the blockchain ledger; and compressing data of the specified portion of the blockchain ledger.