The encryption type for password protected Open XML files must be set.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-17619	DTOO189	SV-52726r3_rule		Medium

Description
If unencrypted files are intercepted, sensitive information in the files can be compromised. To protect information confidentiality, Microsoft Office application files can be encrypted and password protected. Only users who know the correct password will be able to decrypt such files. Since some encryption types are less secure and easier to breach, Microsoft Enhanced RSA and AES Cryptographic Provider, AES-256, 256-bit should be used when encrypting documents.

Description

If unencrypted files are intercepted, sensitive information in the files can be compromised. To protect information confidentiality, Microsoft Office application files can be encrypted and password protected. Only users who know the correct password will be able to decrypt such files. Since some encryption types are less secure and easier to breach, Microsoft Enhanced RSA and AES Cryptographic Provider, AES-256, 256-bit should be used when encrypting documents.

STIG	Date
Microsoft Office System 2013 STIG	2017-06-20

Details

Check Text ( C-47054r5_chk )
Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Office 2013 >> Security Settings "Encryption type for password protected Office Open XML files" is set to "Enabled (Microsoft Enhanced RSA and AES Cryptographic Provider, AES 256,256)". Use the Windows Registry Editor to navigate to the following hive: HKEY_Users For every users profile hive under HKEY_Users, navigate to the following key: \Software\Policies\Microsoft\Office\15.0\common\security If the value “OpenXMLEncryption” is REG_SZ = "Microsoft Enhanced RSA and AES Cryptographic Provider, AES 256,256" for every user profile hive, this is not a finding.

Check Text ( C-47054r5_chk )

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Office 2013 >> Security Settings "Encryption type for password protected Office Open XML files" is set to "Enabled (Microsoft Enhanced RSA and AES Cryptographic Provider, AES 256,256)".

Use the Windows Registry Editor to navigate to the following hive:
HKEY_Users

For every users profile hive under HKEY_Users, navigate to the following key:
\Software\Policies\Microsoft\Office\15.0\common\security

If the value “OpenXMLEncryption” is REG_SZ = "Microsoft Enhanced RSA and AES Cryptographic Provider, AES 256,256" for every user profile hive, this is not a finding.

Fix Text (F-45651r2_fix)
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Office 2013 -> Security Settings "Encryption type for password protected Office Open XML files" to "Enabled (Microsoft Enhanced RSA and AES Cryptographic Provider,AES 256,256)".