Stored public key validity registers for cryptographic devices and systems
Systems and techniques for performing cryptographic operations based on public key validity registers are described. A described system includes a controller and a memory structure to store one or more public keys. The memory structure includes one or more validity registers that respectively correspond to the one or more public keys. The controller has exclusive write access to the validity register. The controller can be configured to perform an authentication of a public key, write an authentication status value to the corresponding validity register based on a result of the authentication, and perform one or more cryptographic operations using the public key that are conditional on the validity register indicating an authenticated status for the public key.
1. An apparatus comprising:
a memory structure to store a public key, wherein the memory structure comprises a validity register that corresponds to the public key; and
a controller configured to perform an authentication of the public key, write an authentication status value to the validity register based on a result of the authentication, the authentication status value corresponding to one of an authenticated status for the public key or an unauthenticated status for the public key, and perform one or more cryptographic operations using the public key that are conditional on the validity register indicating the authenticated status for the public key, wherein the apparatus has exclusive write access to the validity register,
wherein the validity register comprises two or more bits, and the controller is configured to write the authentication status value to each of the two or more bits, and
wherein the controller is configured to read the two or more bits from the validity register to determine an authentication status for the public key based on at least one of whether a majority agreement of the two or more bits indicates the authenticated status for the public key or whether any bit of the two or more bits indicates the unauthenticated status for the public key.
2. The apparatus of claim 1 , further comprising:
a host interface to communicate with a host, wherein the controller is configured to receive a command from the host via the host interface, the command indicating a cryptographic operation to be performed by the apparatus using the public key.
3. The apparatus of claim 2 , wherein the controller is configured to send a failure code to the host in response to the command if the validity register indicates the unauthenticated status for the public key.
4. The apparatus of claim 1 , further comprising:
a host interface to communicate with a host, wherein the controller is configured to grant the host read-only access to the validity register.
5. The apparatus of claim 1 , wherein the controller is configured to write an unauthenticated status value to the validity register in response to changing the public key.
6. The apparatus of claim 1 , further comprising:
an integrated circuit that comprises the memory structure and the controller.
7. The apparatus of claim 1 , wherein the memory structure contains a non-volatile memory, wherein the memory structure stores a plurality of public keys and corresponding validity registers in the non-volatile memory.
8. The apparatus of claim 1 , wherein the memory structure stores a first public key associated with a first validity register and a first parent key pointer and a second public key associated with a second validity register and a second parent key pointer,
wherein the second parent key pointer of the second public key is a multi-bit pointer to the first public key, and
wherein the controller is configured to write an unauthenticated status value to the second validity register in response to updating the first public key, the unauthenticated status value corresponding to an unauthenticated status for the second key.
9. The apparatus of claim 8 , wherein the memory structure is configured to store a first key configuration slot for the first public key, the first key configuration slot including at least one of an access permission list to allow or deny access or use of the first public key, a value indicating that the first public key has to be authenticated prior to use, or one or more bits indicating a policy of whether a random nonce is required for an authentication of the first public key.
10. The apparatus of claim 8 , wherein the controller is configured to:
generate a nonce in response to receiving a nonce command from a host via a host interface in the controller;
generate, by using a hash function, a hash of the nonce and the second public key in response to receiving a command to authenticate the second public key from the host, the second public key being generated based on the first public key;
produce, by using a verification algorithm, an authentication result based on the hash and the first public key; and
write a second authentication status value for the second public key to the second validity register based on the authentication result.
11. A method comprising:
retrieving a public key stored in a memory structure;
performing an authentication of the public key to determine an authentication status value, the authentication status value corresponding to one of an authenticated status for the public key or an unauthenticated status for the public key;
writing the authentication status value to a validity register of the memory structure that corresponds to the public key; and
performing one or more cryptographic operations using the public key that are conditional on the validity register indicating an authenticated status for the public key,
wherein the validity register comprises two or more bits,
wherein writing the authentication status value comprises writing the authentication status value to each of the two or more bits, and
wherein performing one or more cryptographic operations comprises reading the two or more bits from the validity register to determine the authentication status for the public key based on at least one of whether a majority agreement of the two or more bits indicates the authenticated status for the public key or whether any bit of the two or more bits indicates the unauthenticated status for the public key.
12. The method of claim 11 , further comprising:
receiving a command from a host, the command indicating a cryptographic operation to be performed using the public key.
13. The method of claim 12 , wherein performing one or more cryptographic operations comprises sending a failure code to the host in response to the command if the validity register indicates the unauthenticated status for the public key.
14. The method of claim 11 , further comprising:
writing an unauthenticated status value to the validity register in response to changing the public key.
15. The method of claim 11 , further comprising:
generating a nonce in response to receiving a nonce command from a host via a host interface;
generating, by using a hash function, a hash of the nonce and a second public key in response to receiving a command to authenticate the second public key from the host, the second public key being generated based on the public key;
producing, by using a verification algorithm, an authentication result based on the hash and the public key; and
writing a second authentication status value for the second public key to a second validity register for the second public key based on the authentication result.
16. A system comprising:
a host; and
a cryptographic device that comprises (i) a host interface to communicate with the host and (ii) a memory structure to store a public key and a validity register that corresponds to the public key, wherein the cryptographic device has exclusive write access to the validity register,
wherein the cryptographic device is configured to (i) perform an authentication of the public key, (ii) write an authentication status value to the validity register based on a result of the authentication, the authentication status value corresponding to one of an authenticated status for the public key or an unauthenticated status for the public key, (iii) receive a command from the host via the host interface, the command indicating a cryptographic operation to be performed by the cryptographic device using the public key, (iv) perform the cryptographic operation based on checking the validity register to determine the authentication status for the public key, and (v) send a failure code to the host in response to the command based on the validity register indicating the unauthenticated status for the public key,
wherein the validity register comprises two or more bits, and the cryptographic device is configured to write the authentication status value to each of the two or more bits, and
wherein the cryptographic device is configured to read the two or more bits from the validity register to determine an authentication status for the public key based on at least one of whether a majority agreement of the two or more bits indicates the authenticated status for the public key or whether any bit of the two or more bits indicates the unauthenticated status for the public key.
17. The system of claim 16 , wherein the cryptographic device is configured to grant the host read-only access to the validity register.
18. The system of claim 16 , wherein host is configured to load the public key in to the cryptographic device, wherein the cryptographic device is configured to write an unauthenticated status value to the validity register in response to the public key being loaded.
19. The system of claim 16 , wherein the memory structure stores a plurality of public keys, and wherein the memory structure comprises validity registers that respectively correspond to the public keys.
20. The system of claim 16 , wherein the cryptographic device is configured to:
generate a nonce in response to receiving a nonce command from the host via the host interface;
generate, by using a hash function, a hash of the nonce and a second public key in response to receiving a command to authenticate the second public key from the host, the second public key being generated based on the public key;
produce, by using a verification algorithm, an authentication result based on the hash and the public key; and
write a second authentication status value for the second public key to a second validity register for the second public key based on the authentication result.