A method is described for encrypting data that provides increase resistance to brute force attacks by parallel computing means, such as by a quantum computer. To encrypt the data, it is separated into a plurality of data segments, and each of the data segments is encrypted using a different encryption key. The encrypted data segments are then arranged as an encrypted data file in a manner that impedes parallel attack of the encrypted data segments. For example, the lengths of the encrypted data segments may be non-uniform and/or the spacing of the encrypted data segments within the encrypted data file may be non-uniform. Each encrypted segment may contain a pointer to the next segment, thus permitting an authorised recipient to sequentially decrypt the data file without prior knowledge of the lengths and/or spacings of the encrypted data segments.