1. A computer-implemented method of secure data deletion, comprising: providing a master cryptographic key securely stored on an internal storage of a hardware security module of an apparatus; providing a plurality of data objects individually encrypted and stored on a storage medium of the apparatus, the storage medium further storing a hierarchical data-maintenance structure comprising a tree having successive nodes including a root node, a plurality of hash-nodes, and a plurality of partition tables, the root node decipherable via the master cryptographic key; responsive to receiving an instruction specifying to delete a first of the plurality of data objects, wherein the first object is assigned to a first of the partition tables, wherein the first object is decipherable via a first cryptographic key stored in the first partition table, traversing successive nodes in the tree by successively decrypting one or more of the plurality of hash-nodes, and the first partition table starting from the root node and using cryptographic keys obtained by decrypting each of the traversed nodes; and recursively traversing and re-encrypting successive nodes starting from the first partition table and with new cryptographic keys, by operation of one or more computer processors, wherein the first cryptographic key is removed from the first partition table or disregarded in re-encrypting the first partition table, thereby effecting secure deletion of the first data object.