| 摘要 |
A method of applying encryption to a set of ordinally numbered portions of data, comprises: producing an ordinally numbered set of encryption codes in accordance with a binary tree structure having L levels l where l is 0, 1, 2 ....L, each level having 2<l> nodes, each node in level l being linked to two nodes in the next higher level l + 1 and one node in the next lower level l - 1, the number of levels L being such that level L has a number 2<L> nodes not less than the number of said portions of data, each node of level l having associated therewith an encryption code generated from the encryption code associated with the node of level l-1 with which it is linked; and applying the respective encryption codes of level L to respective ones of the said portions of data. A method of decrypting a predetermined subset of portions of data encrypted by the encryption comprises specifying a sub-set of the ordinally numbered portions; generating decryption codes for decrypting the said subset of encrypted portions receiving the said decryption data; generating from the said decryption data the decryption codes of the said subset of portions of data; and decrypting the said portions of the said subset using the generated decryption codes. |
