2.2.6 Encryption and Obfuscation (Password to Open)
A file in Word Binary File Format can be password protected by using one of the following mechanisms:
XOR obfuscation (section 188.8.131.52)
Office binary document RC4 encryption (section 184.108.40.206)
Office binary document RC4 CryptoAPI encryption<7> (section 220.127.116.11)
If FibBase.fEncrypted and FibBase.fObfuscated are both 1, the file is obfuscated by using XOR obfuscation (section 18.104.22.168) as specified in section 22.214.171.124.
If FibBase.fEncrypted is 1 and FibBase.fObfuscated is 0, the file is encrypted by using either Office Binary Document RC4 Encryption (section 126.96.36.199) or Office Binary Document RC4 CryptoAPI Encryption (section 188.8.131.52), with the EncryptionHeader stored in the first FibBase.lKey bytes of the Table stream. The EncryptionHeader.EncryptionVersionInfo specifies which encryption mechanism was used to encrypt the file.
See Security Considerations for information about security concerns relating to file obfuscation and encryption for this file format.