2.4.2.2 Binary Document Write Protection Method 2
Binary documents that conform to the file format as specified in [MS-XLS] MUST store the write protection password verifier in the file, as specified in [MS-XLS] section 2.2.9 and created by using the method specified in section 2.3.7.1. When a binary document using write protection method 2 is write protected, the document can also be encrypted by using one of the methods specified in section 2.3.<25>