# US 11,115,208 B2 · Protecting sensitive information from an authorized device unlock

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- Number: US 11,115,208 B2
- Document ID: US11115208B2
- Status: Granted
- Kind: B2
- Application number: 16/951,553
- Filed: 2020-11-18
- Published: 2021-03-11
- Granted: 2021-09-07
- Earliest claimed: 2016-11-10
- Applicants: Ernest Brickell
- Inventors: Ernest Brickell
- Web page: https://patentgrep.com/patent/US11115208B2

## CPC

- H04L 9/0894: {Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage}
- G06F 21/53: by executing in a restricted environment, e.g. sandbox or secure virtual machine
- G06F 21/572: {Secure firmware programming, e.g. of basic input output system [BIOS]}
- G06F 21/602: {Providing cryptographic facilities or services}
- G06F 21/62: Protecting access to data via a platform, e.g. using keys or access control rules
- G06F 21/71: to assure secure computing or processing of information
- H04L 9/0643: {Hash functions, e.g. MD5, SHA, HMAC or f9 MAC}
- H04L 9/0819: {Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) (network architectures or network communication protocols for key distribution in a packet data network H04L63/062)}
- H04L 9/0869: {involving random numbers or seeds}
- H04L 9/0897: {involving additional devices, e.g. trusted platform module [TPM], smartcard or USB}
- H04L 9/3247: {involving digital signatures}
- H04L 9/50: {using hash chains, e.g. blockchains or hash trees}
- H04L 63/06: {for supporting key management in a packet data network (cryptographic mechanisms or cryptographic arrangements for key management H04L9/08)}
- H04L 63/062: {for key distribution, e.g. centrally by trusted party (cryptographic mechanisms or cryptographic arrangements for key distribution involving a central third party H04L9/0819)}
- H04L 63/10: {for controlling access to devices or network resources}
- H04L 63/105: {Multiple levels of security}
- H04W 12/04: Key management, e.g. using generic bootstrapping architecture [GBA]
- H04W 12/086: using security domains
- G06F 21/31: User authentication
- G06F 2221/2101: Auditing as a secondary aspect
- G06F 2221/2105: Dual mode as a secondary aspect
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

Methods and apparati for auditing uses of cryptographic keys. In a method embodiment of the present invention, a set of audited uses for a cryptographic key is defined; the key is generated inside a protected execution environment of a digital computer; all software and firmware that is usable in the execution environment to access the key is demonstrated to an auditor; and, for each audited use of the key, a non-tamperable audit record describing said use is released.

## Claims

### Claim 1

A computing device comprising:
a first partition in which only applications authorized by a cryptographic verification performed on the computing device can execute;
a second partition in which applications can execute without the authorization required by the first partition;
an unlocking component comprising two modules for unlocking the device, a primary unlock module, and an authorized external unlock module; and
coupled to the first and second partitions, a resource protection module configured to prevent protected data of applications authorized to execute in the first partition from being accessed by applications executing in the second partition; wherein
the resource protection module is further configured to prevent protected data of applications authorized to execute in the first partition from being accessed by applications executing in the second partition conditioned upon the device having been unlocked using the authorized external unlock module; and
the authorized external unlock module comprises an unlock verification key and a verification module for verifying a digital signature using the unlock verification key, wherein the verification module is configured to verify the digital signature before issuing a valid unlock command.

### Claim 2 (depends on 1)

The computing device of claim 1, further comprising, coupled to said first partition, an application authorization module having access to an application verification key, wherein said application authorization module is configured to verify a digitally signed request to execute an application in the first partition using the application verification key.

### Claim 3 (depends on 1)

The computing device of claim 1, further comprising an output module, wherein any successful unlock using the authorized external unlock module is recorded in the output module.

### Claim 4

Method for unlocking a locked computing device having first and second partitions for executing applications, said method comprising a partition protection technique and first and second unlocking techniques, wherein:
the partition protection technique prevents applications executing in the second partition from accessing data of applications executing in the first partition;
the first unlocking technique comprises unlocking the device through entry of a user password which allows access to both partitions;
the second unlocking technique comprises unlocking the device through an authorized external unlock method which allows access to only the second partition, access to the first partition being denied; and
the authorized external unlock method comprises employing an unlock verification key and a verification module for verifying a digital signature using the unlock verification key, wherein the verification module is configured to verify the digital signature before issuing a valid unlock command.

### Claim 5 (depends on 4)

Method of claim 4, further comprising a step of verifying a digital signature for applications that execute in the first partition when the device is unlocked through the authorized external unlock method.

### Claim 6 (depends on 4)

Method of claim 4, wherein the second unlocking technique further comprises the step of recording any unlock of the device made through the authorized external unlock method.