Abstract: Embodiments of the disclosure provide blockchain-implemented methods and systems for secure data transfer and/or storage via the use of data hiding (e.g. steganography algorithms, watermarking etc). In accordance with one aspect, a data hiding algorithm is applied multiple times to a portion of secret data to embed it in a cover file. This constructs layers of hidden data, e.g. secret data hidden in an image that is then used as secret data in a further cover file and so on. Each layer can incorporate encryption and authentication techniques to further enhance security. The final layer or a compressed version is provided within a blockchain transaction. Additionally or alternatively, the secret data can be split into a plurality of shares. This can be achieved using a splitting scheme such as, for example Shamir's Secret Sharing Scheme. Different shares of the secret data can then be encrypted before being hidden within a cover file.