Abstract: The present invention concerns a computer-implemented method for secure data exchange between a sender (A) and a recipient (B), wherein the method is performed by the sender (A) and comprises encrypting data using a symmetric key k, creating a write transaction TW, wherein the write transaction TW comprises information usable to derive the symmetric key k and an access policy identifying the recipient (B) as being allowed to decrypt the encrypted data, providing the recipient (B) access to the encrypted data, and sending the write transaction TW to a first group of servers (AC) for being stored in a blockchain data structure maintained by the first group of servers (AC).

Abstract: Data storage and retrieval systems, methods, and computer-readable media utilize a cryptographically verifiable data structure that facilitates verification of a transaction in a decentralized peer-to-peer environment using multi-hop backwards and forwards links. Backward links are cryptographic hashes of past records. Forward links are cryptographic signatures of future records that are added retroactively to records once the target block has been appended to the data structure.

Abstract: Data storage and retrieval systems, methods, and computer-readable media utilize a cryptographically verifiable data structure that facilitates verification of a transaction in a decentralized peer-to-peer environment using multi-hop backwards and forwards links. Backward links are cryptographic hashes of past records. Forward links are cryptographic signatures of future records that are added retroactively to records once the target block has been appended to the data structure.