2.1.426 Part 1 Section 17.15.1.93, writeProtection (Write Protection)

For additional notes that apply to this portion of the standard, please see the notes for documentProtection, §17.15.1.29(a, b,d, e).

a.   The standard states that this setting is keyed off of a non-existent password attribute.

Word uses the AG_Password attribute group to determine whether to prompt for a password.

b.   The standard states that this setting uses a specific set of attributes, specified by the AG_Password attribute group, to store the password hash.

In Office, when the HKCU/Software/Microsoft/Office/<VERSION>/Common/Security/UseIsoPasswordVerifier registry key is set to 1, the XML for file sharing is written by using the XML attribute structure in the following table.

Name	Description
algorithm Name	The name of the cryptographic hashing algorithm used to generate the hash value. Only those algorithms that are installed in the operating system’s cryptographic subsystem can be utilized by Office. The following hash algorithm names are reserved: MD2 Specifies that the MD2 algorithm, as defined by RFC 1319, shall be used. [Note: It is recommended that applications should avoid using this algorithm to store new hash values, because of publicly known breaks. end note] MD4 Specifies that the MD4 algorithm, as defined by RFC 1320, shall be used. [Note: It is recommended that applications should avoid using this algorithm to store new hash values, because of publicly known breaks. end note] MD5 Specifies that the MD5 algorithm, as defined by RFC 1321, shall be used. [Note: It is recommended that applications should avoid using this algorithm to store new hash values, because of publicly known breaks. end note] RIPEMD-128 Specifies that the RIPEMD-128 algorithm, as defined by ISO/IEC 10118-3:2004 shall be used. [Note: It is recommended that applications should avoid using this algorithm to store new hash values, because of publicly known breaks. end note] RIPEMD-160 Specifies that the RIPEMD-160 algorithm, as defined by ISO/IEC 10118-3:2004, shall be used. SHA-1 Specifies that the SHA-1 algorithm, as defined by ISO/IEC 10118-3:2004, shall be used. SHA-256 Specifies that the SHA-256 algorithm, as defined by ISO/IEC 10118-3:2004, shall be used. SHA-384 Specifies that the SHA-384 algorithm, as defined by ISO/IEC 10118-3:2004, shall be used. SHA-512 Specifies that the SHA-512 algorithm, as defined by ISO/IEC 10118-3:2004, shall be used. WHIRLPOOL Specifies that the WHIRLPOOL algorithm, as defined by ISO/IEC 10118-3:2004, shall be used.
hash Value	Specifies the hash value for the password required to edit this worksheet. This value shall be compared with the resulting hash value after hashing the user-supplied password using the algorithm specified by the preceding attributes and parent XML element. If the two values match, the protection shall no longer be enforced. If this value is omitted, then the reservationPassword attribute shall contain the password hash for the workbook. [Example: Consider an Office Open XML document with the following information stored in one of its protection elements: <… algorithmName="SHA-1" hashValue="9oN7nWkCAyEZib1RomSJTjmPpCY=" /> The hashValue attribute value of 9oN7nWkCAyEZib1RomSJTjmPpCY= specifies that the user-supplied password must be hashed using the pre-processing defined by the parent element (if any) followed by the hashing algorithm (specified via the algorithmName attribute value) and that the resulting hash value must be match for the protection to be disabled. end example] The possible values for this attribute are defined by the W3C XML Schema base64Binary datatype.
saltValue	Specifies the random bytes that are pre-pended to the user-supplied password before it was hashed by the hashing algorithm.
spinCount	Specifies the number of times the hashing function shall be iteratively run (using each iteration's result as the input for the next iteration).

[Example:

Consider an Office Open XML document with the following information stored in one of its protection elements:

< … algorithmName="SHA-1" hashValue="9oN7nWkCAyEZib1RomSJTjmPpCY=" />

The algorithmName attribute value of SHA-1 specifies that the SHA-1 hashing algorithm must be used to generate a hash from the user-defined password.

end example]

c.   The standard states that all attributes within AG_Password are optional

If any attribute specified by AG_Password is present, Word will require these attributes to be present: algorithmName, hashValue, spinCount. Otherwise, Word will not open the file.