Systems, methods, and apparatus for validating product keys. In some embodiments, a product key includes security information and identification information identifying at least one copy of a software product. The security information may include a first portion to be processed by a first validation authority using first validation information and a second portion to be processed by a second validation authority using second validation information. The second validation information may be stored separately from the first validation information and may not be accessible to the first validation authority. In some embodiments, the first validation authority randomly determines whether a product key is to be audited by the second validation authority. Alternatively, the first validation authority may determine whether to audit based on a type of the software product associated with the product key and/or a perceived level of security risk.