Method and apparatus for distributing encrypted device unique credentials

1 . A method of providing credentials to a device including a chip, the method comprising:

receiving the credentials in credential provisioning server (CPS), the credentials having information encrypted according to a secure server key (SSK) securely stored in a hardware security module (HSM) communicatively coupled to the CPS, the hardware security module also securely storing a master key;

receiving a credential request in the CPS, the credential request comprising a chip identifier that identifies the chip;

securely decrypting the encrypted information in the HSM according to the SSK;

securely deriving a chip-unique key in the HSM, according to the chip identifier and the master key;

re-encrypting the decrypted information according to the computed chip-unique key; and

providing the credentials having the re-encrypted information to the device;

wherein:

the chip included in the device is pre-provisioned during chip manufacturing with:

the chip identifier;

a one-time programmable (OTP) secret key associated with the chip identifier; and

the chip-unique key is computed at least in part from the OTP secret key.

2 . The method of claim 1 , wherein:

the master key is pre-provisioned to the HSM;

the HSM includes a secure processing environment; and

the encrypted information is securely decrypted in the secure processing environment and the chip-unique key is securely derived in the secure processing environment.

3 . The method of claim 2 , wherein:

the HSM is constrained to operate on HSM session key objects solely within the secure processing environment; and

the encrypted information comprise a plurality of encrypted segments, each of the plurality of encrypted segments comprising:

a credential key;

an integrity check value; and

padding bytes sufficient to render the encrypted information a same number of bytes as an HSM session key object.

4 . The method of claim 2 , wherein the chip-unique key is the OTP secret key.

5 . The method of claim 2 , wherein:

the credentials further comprise authentication data computed according to the OTP secret key; and

the method further comprises authenticating the credentials in the chip according to the OTP secret key.

6 . The method of claim 2 , wherein securely computing the chip-unique key in the HSM according to the chip identifier and the master key comprises:

computing the OTP secret key from the master key and an chip identifier; and

computing the chip-unique key from the OTP secret key.

7 . The method of claim 6 , wherein:

the chip securely computes the chip-unique key from the OTP secret key according to a first secret sequence; and

the HSM securely computes the chip-unique key according to a second secret sequence complimentary to first secret sequence.

8 . The method of claim 7 , wherein deriving the chip-unique key includes performing a plurality of one-way functions, wherein:

a first function is performed according to the OTP secret key; and

each subsequent function uses a result of each preceding function as a secret key.

9 . The method of claim 8 , wherein:

at least one of the one-way functions performed is a decryption operation; and

the OTP secret key is a decryption key.

10 . The method of claim 8 , wherein at least one of the one-way functions is a one-way message authentication code (MAC) operation.

11 . The method of claim 2 , wherein:

the HSM is constrained to operate on HSM session key objects solely within the secure processing environment; and

the encrypted information comprise a plurality of encrypted segments, each of the plurality of encrypted segments comprising:

a credential key;

an integrity check value; and

padding bytes sufficient to render the encrypted information a same number of bytes as an HSM session key object;

securely decrypting the encrypted information in the HSM according to the SSK comprises:

securely decrypting each of the encrypted segments according to the SSK;

securely computing the chip-unique key in the HSM, according to the chip identifier and the master key comprises:

computing the OTP secret key from the master key and an chip identifier; and

computing the chip-unique key for each of the plurality of segments from the OTP secret key,

re-encrypting the decrypted information according to the computed chip-unique key comprises:

re-encrypting each of the plurality of segments according to the chip-unique key associated with each segment.

12 . The method of claim 11 , wherein:

the method further comprises computing a further chip unique key; and

the integrity check value is computed according to the further chip unique key.

13 . The method of claim 11 , wherein:

the chip securely computes the chip-unique key for each of the plurality of segments from the OTP secret key.

14 . An apparatus for providing credentials to a device including a chip, comprising:

a processor; and

a memory, communicatively coupled to the processor, the memory storing processor instructions comprising processor instructions for:

receiving the credentials in credential provisioning server (CPS), the credentials having information encrypted according to a secure server key (SSK) securely stored in a hardware security module (HSM) communicatively coupled to the CPS, the hardware security module also securely storing a master key;

receiving a credential request in the CPS, the credential request comprising a chip identifier that identifies the chip;

securely decrypting the encrypted information in the HSM according to the SSK;

securely computing a chip-unique key in the HSM, according to the chip identifier and the master key;

re-encrypting the decrypted information according to the computed chip-unique key; and

providing the credentials having the re-encrypted information to the device;

wherein:

the chip included in the device is pre-provisioned during chip manufacturing with:

the chip identifier;

a one-time programmable (OTP) secret key associated with the chip identifier; and

the chip-unique key is computed at least in part from the OTP secret key.

15 . The apparatus of claim 14 , wherein:

the master key is pre-provisioned to the HSM;

the HSM includes a secure processing environment; and

the encrypted information is securely decrypted in the secure processing environment and the chip-unique key is securely derived in the secure processing environment.

16 . The apparatus of claim 15 , wherein:

the HSM is constrained to operate on HSM session key objects solely within the secure processing environment; and

the encrypted information comprise a plurality of encrypted segments, each of the plurality of encrypted segments comprising:

a credential key;

an integrity check value; and

padding bytes sufficient to render the encrypted information a same number of bytes as an HSM session key object.

17 . The apparatus of claim 15 , wherein the chip-unique key is the OTP secret key.

18 . The apparatus of claim 15 , wherein the processor instructions for securely computing the chip-unique key in the HSM according to the chip identifier and the master key comprise processor instructions for:

computing the OTP secret key from the master key and an chip identifier; and

computing the chip-unique key from the OTP secret key.

19 . The apparatus of claim 15 , wherein:

the HSM is constrained to operate on HSM session key objects solely within the secure processing environment; and

the encrypted information comprises a plurality of encrypted segments, each of the plurality of encrypted segments comprising:

a credential key;

an integrity check value; and

padding bytes sufficient to render the encrypted information a same number of bytes as an HSM session key object;

the processor instructions for securely decrypting the encrypted information in the HSM according to the SSK comprise processor instructions for:

securely decrypting each of the encrypted segments according to the SSK;

the processor instructions for securely computing the chip-unique key in the HSM, according to the chip identifier and the master key comprise processor instructions for:

computing the OTP secret key from the master key and an chip identifier; and

computing the chip-unique key for each of the plurality of segments from the OTP secret key,

the processor instructions for re-encrypting the decrypted information according to the computed chip-unique key comprise processor instructions for:

re-encrypting each of the plurality of segments according to the chip-unique key associated with each segment.

20 . An apparatus for providing credentials to a device including a chip, comprising:

means for receiving the credentials in credential provisioning server (CPS), the credentials having information encrypted according to a secure server key (SSK) securely stored in a hardware security module (HSM) communicatively coupled to the CPS, the hardware security module also securely storing a master key;

means for receiving a credential request in the CPS, the credential request comprising a chip identifier that identifies the chip;

means for securely decrypting the encrypted information in the HSM according to the SSK;

means for securely computing a chip-unique key in the HSM, according to the chip identifier and the master key;

means for re-encrypting the decrypted information according to the computed chip-unique key; and

means for providing the credentials having the re-encrypted information to the device;

wherein:

the chip included in the device is pre-provisioned during chip manufacturing with:

the chip identifier;

a one-time programmable (OTP) secret key associated with the chip identifier; and

the chip-unique key is derived at least in part from the OTP secret key.