Secure key exchange using key-associated attributes

A system comprising:

• a processor;
• memory storing instructions that, when executed, cause operations comprising:
• receiving, from an external server and at an interface between an access and tamper resistant circuit block and exposed circuitry, a request for a combined authorization key;
• and
• within the access and tamper resistant circuit block:
• based on the received request, retrieving two or more keys from key portions of a hardware enforced key register, each retrieved key generated within the access and tamper resistant circuit block, and retrieving associated key attributes for each retrieved key from attribute portions of the hardware enforced key register, each key attribute encoding one or more designated operations that can be performed on the retrieved key associated with the key attribute, wherein contents of the key portions of the hardware enforced key register are not readable in unencrypted form, and wherein contents of the attribute portions of the hardware enforced key register are readable in unencrypted form;
• using a mixing algorithm, combining the two or more retrieved keys with attributes for the combined authorization key to generate the combined authorization key, wherein the associated key attributes for each key provide permission to combine using the mixing algorithm;
• and
• storing the combined authorization key and associated key attributes for the combined authorization key in the hardware enforced key register.

A device comprising:

• an interface between an access and tamper resistant circuit block and exposed circuitry;
• and
• memory storing instructions that, when executed, cause operations comprising:
• receiving, at the interface and from an external server, a request for a combined authorization key;
• and
• within the access and tamper resistant circuit block:
• based on the received request, retrieving two or more keys from key portions of a hardware enforced key register, each retrieved key generated within the access and tamper resistant circuit block, and retrieving associated key attributes for each retrieved key from attribute portions of the hardware enforced key register, each key attribute encoding one or more designated operations that can be performed on the retrieved key associated with the key attribute, wherein contents of the key portions of the hardware enforced key register are not readable in unencrypted form, and wherein contents of the attribute portions of the hardware enforced key register are readable in unencrypted form;
• using a mixing algorithm, combining the two or more retrieved keys with attributes for the combined authorization key to generate the combined authorization key, wherein the associated key attributes for each key provide permission to combine using the mixing algorithm;
• and
• storing the combined authorization key and associated key attributes for the combined authorization key in the hardware enforced key register.