2.3.4 ECMA-376 Document Encryption
When an ECMA-376 document [ECMA-376] is encrypted as specified in [ECMA-376] Part 2 Annex C Table C-5 BIT 0, a structured storage utilizing the data spaces construct as specified in section 2.1 MUST be used. Unless exceptions are noted in the following subsections, streams (1) and storages contained within the \0x06DataSpaces storage MUST be present as specified in section 2.1.1.