A method, article, and system for providing an effective implementation of a data structure comprising instructions that are cryptographically protected against alteration or misuse, wherein the instructions further comprise a trusted block that defines specific key management policies that are permitted when an application program employs the trusted block in application programming interface (API) functions to generate or export symmetric cryptographic keys. The trusted block has a number of fields containing rules that provide an ability to limit how the trusted block is used, thereby reducing the risk of the trusted block being employed in unintended ways or with unintended keys.