Abstract: Persistent protection for application-specific or dependent software such as a workbook for use with independent software (such as Excel™) includes encryption of at least some instructions or other key information before distribution hence providing intellectual property security and (optionally) location security. The cooperative decoder module provides means for secure and controlled decryption of the secured content, if the cooperative security module has confirmed an authorised environment. The invention provides persistent security such that the secured content remains encrypted and is barred from access such as by a hacker, so cannot feasibly be amended or published.