Future constraints for hierarchical chain of trust

A non-transitory storage medium storing a computer program comprising program instructions to control an electronic device to:

• receive a domain configuration command requesting configuration of a target domain of a hierarchical chain of trust on the electronic device, the target domain providing a cryptographic identity for authenticating commands to be executed by the electronic device, and the domain configuration command specifying at least one target domain constraint to be satisfied by commands to be authenticated by the target domain and at least one target domain future constraint to be combined with other constraints when configuring a descendant domain of the target domain;
• authenticate the domain configuration command based on a cryptographic identity provided by an authenticating domain, wherein the target domain is the authenticating domain or a descendant domain of the authenticating domain in the hierarchical chain of trust;
• and
• when the domain configuration command is authenticated:
• combine, using one or more logical functions, said at least one target domain constraint and at least one future constraint specified by the authenticating domain to generate a combined constraint set comprising zero, one or more constraints to be satisfied by commands to be authenticated by the target domain, and storing an indication of said combined constraint set, and
• combine, using one or more logical functions, said at least one target domain future constraint and said at least one future constraint specified by the authenticating domain to generate a combined target domain future constraint set comprising zero, one or more constraints to be combined with other constraints when configuring a descendant domain of the target domain, and storing an indication of said combined target domain future constraint set,
• wherein the target domain constraint refers to one or more requirements to be satisfied by a command in order to be authenticated, and
• wherein the future constraint refers to one or more requirements to be satisfied by a command authenticated by one or more descendant domains of the authenticating domain.

An electronic device comprising:

• authentication circuitry configured to receive a domain configuration command requesting configuration of a target domain of a hierarchical chain of trust on the electronic device, the target domain providing a cryptographic identity for authenticating commands to be executed by the electronic device, the domain configuration command specifying at least one target domain constraint to be satisfied by commands to be authenticated by the target domain and at least one target domain future constraint to be combined with other constraints when configuring a descendant domain of the target domain, and to authenticate the domain configuration command based on a cryptographic identity provided by an authenticating domain, wherein the target domain is the authenticating domain or a descendant domain of the authenticating domain in the hierarchical chain of trust;
• wherein when the domain configuration command is authenticated, the authentication circuitry is configured to:
• combine, using one or more logical functions, said at least one target domain constraint and at least one future constraint specified by the authenticating domain to generate a combined constraint set comprising zero, one or more constraints to be satisfied by commands to be authenticated by the target domain, and to store an indication of said combined constraint set, and
• combine, using one or more logical functions, said at least one target domain future constraint and said at least one future constraint specified by the authenticating domain to generate a combined target domain future constraint set comprising zero, one or more constraints to be combined with other constraints when configuring a descendant domain of the target domain, and storing an indication of said combined target domain future constraint set,
• wherein the target domain constraint refers to one or more requirements to be satisfied by a command in order to be authenticated, and
• wherein the future constraint refers to one or more requirements to be satisfied by a command authenticated by one or more descendant domains of the authenticating domain.