# US 2021/0240833 A1 · Security device, electronic device, secure boot management system, method for generating boot image, and method for executing boot chain

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- Number: US 2021/0240833 A1
- Document ID: US20210240833A1
- Status: Published application
- Kind: A1
- Application number: 17/000,748
- Filed: 2020-08-24
- Published: 2021-08-05
- Earliest claimed: 2020-01-30
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Samsung Electronics Co., Ltd.
- Inventors: Ki Seok BAE; Jong Hoon Shin; Ki Tak Kim; Hye Soo Lee; Jin Su Hyun; Hyo Sun Hwang
- Web page: https://patentgrep.com/patent/US20210240833A1

## CPC

- G06F 21/575: {Secure boot}
- G06F 21/572: {Secure firmware programming, e.g. of basic input output system [BIOS]}
- H04L 9/0861: {Generation of secret information including derivation or calculation of cryptographic keys or passwords}
- H04L 9/0897: {involving additional devices, e.g. trusted platform module [TPM], smartcard or USB}
- H04L 9/14: using a plurality of keys or algorithms
- H04L 9/3242: {involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC}
- H04L 9/3247: {involving digital signatures}
- H04L 9/3268: {using certificate validation, registration, distribution or revocation, e.g. certificate revocation list [CRL]}
- G06F 2221/033: Test or assess software
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Provided is a security device, an electronic device, a secure boot management system, a method for generating a boot image and a method for executing a boot chain. The security device includes a key deriver configured to receive a root key and a protected boot key included in a boot image and generate a derived key according to a key protection method using the root key and the protected boot key, a key processor configured to perform verification according to the key protection method using the generated derived key to extract a boot key from the protected boot key included in the boot image, a secure booter configured to perform verification on a protected execution image included in the boot image using the extracted boot key, and a processor configured to execute a verified execution image on which the verification has been completed by the secure booter.

## Claims

### Claim 1

A security device comprising:
a key deriver configured to obtain a root key and a protected boot key included in a boot image, and to generate a derived key according to a key protection method using the root key and the protected boot key;
a key processor configured to perform verification according to the key protection method using the generated derived key, to extract a boot key from the protected boot key included in the boot image;
a secure booter configured to perform verification on a protected execution image included in the boot image using the extracted boot key; and
a processor configured to execute a verified execution image on which the verification has been completed by the secure booter.

### Claim 2 (depends on 1)

The security device of claim 1, further comprising a nonvolatile memory device configured to store the root key.

### Claim 3 (depends on 1)

The security device of claim 1, wherein:
the key protection method includes a first key protection method and a second key protection method which are different from each other; and
the key processor is configured to perform first verification according to the first key protection method and second verification according to the second key protection method, to extract the boot key from the protected boot key.

### Claim 4 (depends on 3)

The security device of claim 3, wherein:
the derived key includes a first derived key generated according to the first key protection method and a second derived key generated according to the second key protection method;
the key processor is configured to perform the first verification according to the first key protection method using the first derived key; and
the key processor is configured to perform the second verification according to the second key protection method using the second derived key.

### Claim 5 (depends on 1)

The security device of claim 1, further comprising:
a volatile internal memory disposed within the security device and storing the verified execution image,
wherein the processor is configured to execute a secure boot chain using the verified execution image stored in the volatile internal memory.

### Claim 6 (depends on 1)

The security device of claim 1, wherein the key processor comprises:
a first sub-key processor configured to decrypt the protected boot key to extract the boot key;
a second sub-key processor configured to perform message authentication code (MAC) verification on the protected boot key to extract the boot key;
a third sub-key processor configured to verify an electronic signature of the protected boot key to extract the boot key; and
a fourth sub-key processor configured to verify a certificate for the protected boot key to extract the boot key.

### Claim 7 (depends on 6)

The security device of claim 6, wherein:
the key deriver comprises:
a first sub-key deriver configured to generate a first derived key for the decryption,
a second sub-key deriver configured to generate a second derived key for the MAC verification,
a third sub-key deriver configured to generate a third derived key for the signature verification, and
a fourth sub-key deriver configured to generate a fourth derived key for the certificate verification;
the first sub-key processor is configured to extract the boot key using the first derived key;
the second sub-key processor is configured to extract the boot key using the second derived key;
the third sub-key processor is configured to extract the boot key using the third derived key; and
the fourth sub-key processor is configured to extract the boot key using the fourth derived key.

### Claim 8

An electronic device comprising:
a storage device configured to store a boot image including a protected boot key and a protected execution image; and
a security device configured to store a root key and perform a boot operation to execute the boot image using the root key,
wherein the security device is configured to:
generate a derived key according to a predetermined key protection method using the root key and the protected boot key,
perform verification according to the predetermined key protection method using the generated derived key to extract a boot key from the protected boot key, and
perform the boot operation using the extracted boot key.

### Claim 9 (depends on 8)

The electronic device of claim 8, wherein the security device is configured to:
perform verification on the protected execution image using the extracted boot key, and
perform the boot operation by executing a verified execution image on which the verification has been completed.

### Claim 10 (depends on 8)

The electronic device of claim 8, wherein:
the storage device is configured to:
at a first time point, store a first boot image including a first protected boot key, and
at a second time point following the first time point, store a second boot image including a second protected boot key different from the first protected boot key; and
the security device is configured to:
store a same root key at the first time point and the second time point,
at the first time point, extract a first boot key using the stored same root key and the first protected boot key and perform the boot operation using the extracted first boot key, and
at the second time point, extract a second boot key using the stored same root key and the second protected boot key and perform the boot operation using the extracted second boot key.

### Claim 11 (depends on 10)

The electronic device of claim 10, wherein the security device is configured to:
at the first time point, generate a first derived key using the stored same root key and the first protected boot key, and extract the first boot key using the generated first derived key, and
at the second time point, generate a second derived key using the stored root key and the second protected boot key, and extract the second boot key using the generated second derived key.

### Claim 12 (depends on 11)

The electronic device of claim 11, wherein the generated first derived key and the generated second derived key are different from each other.

### Claim 13 (depends on 8)

The electronic device of claim 8, wherein:
the storage device is configured to store:
a first boot image including a first protected boot key and a first protected execution image, and
a second boot image including a second protected boot key different from the first protected boot key and a second protected execution image different from the first protected execution image; and
wherein the security device is configured to:
extract a first boot key using the stored root key and the first protected boot key, and perform a first boot operation using the extracted first boot key, and
extract a second boot key using the stored root key and the second protected boot key, and perform a second boot operation using the extracted second boot key.

### Claim 14 (depends on 13)

The electronic device of claim 13, wherein the security device is configured to:
generate a first derived key using the stored root key and the first protected boot key to extract the first boot key using the generated first derived key, and
generate a second derived key using the stored root key and the second protected boot key to extract the second boot key using the generated second derived key.

### Claim 15 (depends on 8)

The electronic device of claim 8, wherein:
the predetermined key protection method includes a first key protection method and a second key protection method which are different from each other; and
the security device is configured to extract the boot key from the protected boot key by performing first verification according to the first key protection method and second verification according to the second key protection method.

### Claim 16 (depends on 15)

The electronic device of claim 15, wherein:
the derived key includes a first derived key generated according to the first key protection method and a second derived key generated according to the second key protection method;
the security device is configured to perform the first verification according to the first key protection method using the first derived key; and
the security device is configured to perform the second verification according to the second key protection method using the second derived key.

### Claim 17

A secure boot management system comprising:
a key deriver configured to receive a root key and a key protection method and generate a derived key according to the received key protection method;
a key protector configured to perform a protection operation on a boot key according to the key protection method using the generated derived key, to generate a protected boot key; and
a boot image generation system configured to perform a protection operation on an execution image using the boot key, and generate a boot image including the protected boot key and the protected execution image.

### Claim 18 (depends on 17)

The secure boot management system of claim 17, wherein:
the key protection method includes a first key protection method and a second key protection method which are different from each other,
the derived key includes a first derived key generated from the root key according to the first key protection method and a second derived key generated from the root key according to the second key protection method, and
the key protector is configured to perform a first protection operation on the boot key according to the first key protection method using the first derived key, and to perform a second protection operation on the boot key according to the second key protection method using the second derived key to generate the protected boot key.

### Claim 19 (depends on 17)

The secure boot management system of claim 17, wherein:
the key deriver is provided with user additional information to generate the derived key; and
the key deriver is configured to generate the derived key using the root key, the key protection method and the user additional information.

### Claim 20 (depends on 17)

The secure boot management system of claim 17, wherein the key protector comprises:
a first sub-key protector configured to perform an encryption operation to generate the protected boot key;
a second sub-key protector configured to generate a message authentication code (MAC) to generate the protected boot key;
a third sub-key protector configured to generate an electronic signature to generate the protected boot key; and
a fourth sub-key protector configured to generate a certificate to generate the protected boot key.

### Claim at position 21

21-26. (canceled)