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:
If FibBase.fEncrypted and FibBase.fObfuscation are both 1, the file is obfuscated by using XOR obfuscation as specified in section 184.108.40.206.
If FibBase.fEncrypted is 1 and FibBase.fObfuscation is 0, the file is encrypted by using either Office Binary Document RC4 Encryption or Office Binary Document RC4 CryptoAPI Encryption as specified in sections 220.127.116.11 and 18.104.22.168, 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.