# US 9,053,341 B2 · Multi-identity for secure file sharing

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- Number: US 9,053,341 B2
- Document ID: US9053341B2
- Status: Granted
- Kind: B2
- Application number: 14/207,856
- Filed: 2014-03-13
- Published: 2014-10-09
- Granted: 2015-06-09
- Earliest claimed: 2013-03-13
- Assignees: nCrypted Cloud LLC
- Applicants: nCrypted Cloud LLC
- Inventors: Igor Odnovorov; Nicholas Stamos
- Web page: https://patentgrep.com/patent/US9053341B2

## CPC

- G06F 21/6218: {to a system of files or objects, e.g. local or distributed file system or database}
- H04L 9/088: {Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms (network architectures or network communication protocols for using time-dependent keys in a packet data network H04L63/068)}
- H04L 9/0891: {Revocation or update of secret information, e.g. encryption key update or rekeying}
- H04L 9/0894: {Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage}
- H04L 63/065: {for group communications (cryptographic mechanisms or cryptographic arrangements for key management involving conference or group key H04L9/0833)}
- H04L 63/102: {Entity profiles}
- G06F 2221/2141: Access rights, e.g. capability lists, access control lists, access tables, access matrices
- H04L 63/0428: {wherein the data content is protected, e.g. by encrypting or encapsulating the payload}
- 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

Techniques for controlling access to shared data files such as stored in a collaborative file sharing service. Organizations want to have access to data originated by their employees and want that access to continue even when the employees leave the company. Also, organizations do not want former employees to have access to the company's files. A file storage service uses an Organization's recovery key while creating a recovery record for a file (which may be stored in a folder), and protected using a Work identity. The individual person who originally creates a file and/or shares a folder securely with others is considered the folder's owner as long as he is part of the same Organization. User's identities are validated upon access. The keys are also purged from a local key store as soon as identity changes are detected. In this way, the folder owner will not be able to decrypt files stored in a folder shared using a Work identity if the identity is canceled by the Organization.

## Claims

### Claim 1

A computer-implemented method for providing controlled collaborative access to a data file comprising:
selectively associating a personal identity or a work identity with a designated folder in which a shared data file originated by an individual user is stored;
when the personal identity is associated with the designated folder,
generating a personal recovery key;
storing the personal recovery key; and
protecting the shared data file with a unique file password generated from (a) the personal recovery key assigned to the designated folder in which the file is located and (b) a unique file identifier; else
when the work identity is associated with the designated folder,
generating a work recovery key;
storing the work recovery key; and
protecting the shared data file with a unique file password generated from (a) the work recovery key assigned to the designated folder in which the file is located and (b) a unique file identifier;
and further:
protecting access to the shared data file using the work recovery key and information concerning a present status of the individual user with respect to an organization associated with the work identity, by further
generating an organization recovery key associated with the organization;
protecting the unique password with the organization recovery key;
revoking the individual user's access to the organization recovery key when the organization no longer approves of the individual user's association with the organization; and
preventing the individual user from revoking access to the shared data file by the organization subsequent to revoking the individual user's access to the shared data file, even when the individual user was an original creator of the shared data file: and
when the personal identity is associated with the designated folder, further preventing access by the organization to the personal recovery key.

### Claim 2 (depends on 1)

The method of claim 1 additionally comprising:
assigning ownership privileges to the folder storing the shared data file, wherein the individual user is granted ownership privileges to the folder as long as the individual user is approved by the organization, but when the organization revokes approval for the individual user, the individual user is no longer granted ownership privileges and ownership privileges for the folder are instead granted to the organization.

### Claim 3 (depends on 2)

The method of claim 2 wherein ownership privileges to the folder are controlled by a collaborative file sharing service that provides a cloud storage service.

### Claim 4 (depends on 2)

The method of claim 2 further comprising:
purging the work identity keys from a local key store accessible by the individual user, such that the individual user is not able to access the shared data file shared using the work identity key when the individual user's access is revoked by the organization.

### Claim 5 (depends on 1)

The method of claim 1 additionally comprising:
protecting a folder containing one or more files to be shared securely by assigning a folder key to the folder, where the folder key is the respective one of the personal recovery key or the work recovery key; and
sharing the one or more files in the folder with other individual users by sharing the folder key.

### Claim 6 (depends on 1)

The method of claim 1 wherein a plurality of work identities are provided to a corresponding plurality of users, and a specific one of the plurality of users is granted access to a data file shared among users associated with the plurality of work related identities only so long as long as the organization associated with the specific individual approves of the specific individual user's access to the data file.

### Claim 7

A system comprising:
one or more network interfaces adapted to communicate data over a computer network;
a processor coupled to the network interfaces and adapted to execute one or more processes; and
a memory configured to store a process executable by the processor, the process when executed operable to:
associate a personal identity or a work identity with a designated folder originated by an individual user according to a selection made by input received from the individual user;
control access to a shared data file stored in the folder using the respective personal identity or the work identity, and information concerning a present status of the individual user with respect to an organization;
when the work identity is selected for the designated folder, to further
grant access to the shared data file associated with the work identity by the individual user, only so long as long as the organization approves of the individual user's access to the shared data file;
revoke access to the shared data file by the individual user when the organization no longer approves of the individual user's association with the organization;
protect the shared data file with a unique password that depends on (a) the work recovery key assigned to the designated folder and (b) a unique file identifier;
protect the unique password with an organization recovery key associated with the organization;
revoke access to the organization recovery key by the individual user when the organization no longer approves of the individual user's association with the organization;
prevent the individual from revoking access to the shared data file by the organization even subsequent to revoking the individual's access to the data file, even when the individual was an original creator of the file; and
when the personal identity is selected for the designated folder,
protect the shared data file with a unique password that depends on (a) the personal recovery key assigned to the designated folder and (b) a unique file identifier; and
prevent access to the personal recovery key by the organization.

### Claim 8 (depends on 7)

The system of claim 7 wherein the individual user is given ownership privileges to access the data file as long as the individual user is authorized by the organization, but when the organization revokes authorization for the file, the individual user is no longer granted ownership privileges and ownership privileges are granted to the organization.

### Claim 9 (depends on 8)

The system of claim 8 additionally comprising a collaborative file sharing service for controlling ownership privileges for the file.

### Claim 10 (depends on 7)

The system of claim 7 wherein one or more keys associated with the work identity are also purged from a local key store accessible by the individual user, such that the individual user is not able to access the shared data file using the work identity as soon as the individual's authorization is canceled by the organization.

### Claim 11 (depends on 7)

The system of claim 7 additionally wherein the processor is further to assign the organization a unique key pair that is used as a recovery key for folders associated with the work identity.

### Claim 12 (depends on 11)

The system of claim 11 wherein the processor is further to, for each individual user associated with an organization, assign a unique key pair that used as a work recovery key for folders associated with a work identity for the individual user.

### Claim 13 (depends on 7)

The system of claim 7 wherein the processor is further to, for a folder containing one or more files to be shared securely, protect the folder by assigning a folder key to the folder, where the folder key is selected from one of a personal identity key and a work identity key, and when the contents of the folder are shared with other individual users, to share the folder key.

### Claim 14 (depends on 7)

The system of claim 7 wherein the processor is further to provide a plurality of work identities to a corresponding plurality of users, and a specific one of the plurality of users is granted access to a data file shared among users associated with the plurality of work identities, but only so long as long as the organization associated with the specific individual approves of the specific individual user's access to the data file.