Microcontroller with secure feature for multiple party code development
Multiple secure environments are established within a system on a chip (SoC) by defining a first secure region within a non-volatile memory in the SoC with a first set of parameters written into a predefined parameter region of the non-volatile memory. A second secure region within the non-volatile memory may be defined at a later time by a second set of parameters written into another predefined parameter region of the non-volatile memory. A security module is initialized each time the SoC is powered on by transferring the first set of parameters and the second set of parameters from the parameter region to the security module in a manner that does not expose the first set of parameters or the second set of parameters to a program being executed by the processor. The multiple secure regions of the SoC are enforced by the security module according to the parameter data.
1. A method for establishing multiple secure environments within a system on a chip (SoC), the method comprising:
defining a first secure region within a non-volatile memory in the SoC by receiving a first set of parameters written into a parameter region of the first secure region;
defining a second secure region within the non-volatile memory of the SoC by receiving a second set of parameters written into a parameter region of the second secure region;
initializing a security module each time the SoC is powered on by transferring the first set of parameters and the second set of parameters from the parameter regions to the security module in a manner that does not expose the first set of parameters or the second set of parameters to a program being executed by the processor; and
enforcing the multiple secure regions of the SoC by the security module according to the first and second sets of parameters, wherein the first set of parameters is protected from change while enforcement of the first secure region is enabled and the second set of parameters is protected from change while enforcement of the second secure region is enabled.
2. The method of claim 1 , wherein the enforcing multiple secure environments comprises:
allowing a first program in the first secure region to call a second program in the second secure region and prohibiting the first program from reading data from the second secure region; and
allowing the second program in the second secure region to call the first program in the first secure region and prohibiting the second program from reading data from the first secure region.
3. The method of claim 1 , further comprising:
storing a first program in the first secure region by an initialization process; and
storing a second program in the second secure region by a different initialization process.
4. The method of claim 1 , further comprising inhibiting all access to a region of the nonvolatile memory that is defined in both the first secure region and the second secure region.
5. The method of claim 1 , wherein the first set of parameters includes a password, further comprising disabling enforcement of the first secure environment after the processor writes a data value into the security module matching the password.
6. The method of claim 1 , further comprising inhibiting access to the first secure region and to the second secure region until after the security module is initialized each time the SoC is powered on.