# US 2022/0286276 A1 · Threshold scheme enabled symmetric key member deletion

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- Number: US 2022/0286276 A1
- Document ID: US20220286276A1
- Status: Published application
- Kind: A1
- Application number: 17/826,137
- Filed: 2022-05-26
- Published: 2022-09-08
- Earliest claimed: 2020-05-15
- Assignees: The Boeing Company
- Applicants: The Boeing Company
- Inventors: Mingyan Li; Douglas A. Stuart; Jai J. Choi; Joshua D. Cazalas
- Web page: https://patentgrep.com/patent/US20220286276A1

## CPC

- H04L 9/085: {Secret sharing or secret splitting, e.g. threshold schemes}
- 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 63/0428: {wherein the data content is protected, e.g. by encrypting or encapsulating the payload}
- H04L 63/065: {for group communications (cryptographic mechanisms or cryptographic arrangements for key management involving conference or group key H04L9/0833)}
- H04L 63/08: {for authentication of entities (cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32)}
- H04L 63/0435: {wherein the sending and receiving network entities apply symmetric encryption, i.e. same key used for encryption and decryption (cryptographic mechanisms or cryptographic arrangements for symmetric key encryption H04L9/06)}
- H04L 2209/805: Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
- H04W 84/18: Self-organising networks, e.g. ad-hoc networks or sensor networks
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

A method of securing, by a managing node, communication in a network of member nodes including a first member node. Communication is secured using a (k, n1) secret sharing scheme during a first phase. The managing node announces a phase shift to a subsequent phase relative to the first phase. The managing node secures communication in the network during the subsequent phase using a (k+x, n2) secret sharing scheme. Each of the member nodes is previously in possession of exactly one corresponding unique share for the second key. The first member node is previously in possession of a first unique share for the second key. The managing node deletes the first member node from the subsequent phase by broadcasting the first unique share for the second key.

## Claims

### Claim 1

A method comprising:
securing, by a managing node, communication in a network of a plurality of member nodes including a first member node, wherein communication is secured using a (k, n1) secret sharing scheme during a first phase, “k” is a first threshold of shares required to resolve a first key used in the first phase, and “n1” is a first total number of shares for the first key;
announcing, by the managing node, a phase shift to a subsequent phase relative to the first phase;
securing, by the managing node, communication in the network during the subsequent phase using a (k+x, n2) secret sharing scheme wherein:
“x” is at least 1, and k+x is a second threshold of shares required to resolve a second key used in the subsequent phase,
“n2” is a second total number of shares for the second key,
each of the plurality of member nodes is previously in possession of exactly one corresponding unique share for the second key, and
the first member node is previously in possession of a first unique share for the second key; and
deleting, by the managing node, the first member node from the subsequent phase by broadcasting the first unique share for the second key and, if previously deleted nodes were previously deleted from the network, also broadcasting additional unique shares for the second key belonging to all previously deleted nodes.

### Claim 2 (depends on 1)

The method of claim 1, wherein, after broadcasting:
the first member node has a duplicate copy of the first unique share for the second key, such that the first member node has (k+x)−1 shares for the second key and cannot resolve the second key,
remaining ones of the plurality of member nodes have k+x shares for the second key, being the exactly one corresponding unique share for the second key plus the first unique share for the second key that was broadcast, and wherein the remaining ones of the plurality of member nodes can resolve the second key.

### Claim 3 (depends on 1)

The method of claim 1, wherein the previously deleted nodes were previously deleted, and wherein the managing node further broadcasts the additional unique shares for the second key belonging to all previously deleted nodes.

### Claim 4 (depends on 1)

The method of claim 1, wherein n1 has a first value equivalent to a second value of n2.

### Claim 5 (depends on 1)

The method of claim 1, further comprising:
receiving, by the managing node, a request to delete the first member node of the plurality of member nodes from the network.

### Claim 6 (depends on 1)

The method of claim 1, further comprising:
receiving, at the managing node, a request to add a new member node to the plurality of member nodes;
authenticating, by the managing node, the new member node;
constructing, by the managing node, a new share vector comprising a set of shares comprising corresponding unique shares for a plurality of keys in future phases; and
distributing, by the managing node, the new share vector to the plurality of member nodes and the new member node.

### Claim 7 (depends on 1)

The method of claim 1, wherein “x” is greater than one.

### Claim 8 (depends on 1)

The method of claim 1, further comprising:
receiving, at the managing node, a request to remove a second member node from the plurality of member nodes, the request to remove the second member node to be performed concurrently with the request to delete the first member node,
wherein the second member node has a second unique share for the second key,
wherein the subsequent phase announced comprises at least two phases past a current phase for the network,
wherein x is equal to a number of phases that the subsequent phase is past the current phase, and
wherein broadcasting further comprises broadcasting the second unique share.

### Claim 9 (depends on 1)

The method of claim 1, further comprising:
receiving, at the managing node, a request to remove a plurality of additional member nodes from the plurality of member nodes, wherein the request to remove the plurality of additional member nodes is to be performed concurrently with the request to delete the first member node;
broadcasting, by the managing node, shares for the second key, for the subsequent phase, of the plurality of additional member nodes; and
broadcasting, by the managing node to the plurality of member nodes, a plurality of gap-filling shares for the second key.

### Claim 10 (depends on 9)

The method of claim 9, wherein the subsequent phase is defined by a ceiling function, and wherein the method further comprises:
calculating, by the managing node, the ceiling function, and wherein broadcasting the plurality of gap-filling shares for the second key comprises
broadcasting a number of gap-filing shares equal to the ceiling function.

### Claim at position 11

-25. (canceled)

### Claim 26 (depends on 1)

The method of claim 1, wherein the network comprises an Internet of Things (IoT) network, and wherein the plurality of member nodes comprise tracking devices, network capable machines, and combinations thereof.

### Claim 27 (depends on 1)

The method of claim 1, wherein the network comprises a Mobile Ad hoc Network (MANET), and wherein the plurality of member nodes comprise at least two devices selected from the group consisting of mobile phones, tablet computers, laptop computers, and special purpose computers.

### Claim 28 (depends on 1)

The method of claim 1, wherein the plurality of member nodes comprise network capable devices that are attached to a plurality of cargo units, and wherein the method further comprises:
tracking the plurality of cargo units using the plurality of member nodes.

### Claim 29 (depends on 28)

The method of claim 28, wherein tracking further comprises:
adding a cargo unit to a list of the plurality of cargo units when a new network capable device, attached to a new cargo unit, is added to the plurality of member nodes.

### Claim 30 (depends on 29)

The method of claim 29, wherein the new network capable device is added to the plurality of member nodes by:
receiving, at the managing node, a request to add the new network capable device to the plurality of member nodes;
authenticating, by the managing node, the new network capable device;
constructing, by the managing node, a new share vector comprising a set of shares comprising corresponding unique shares for a plurality of keys in future phases; and
distributing, by the managing node, the new share vector to the plurality of member nodes and the new network capable device.

### Claim 31 (depends on 28)

The method of claim 28, wherein tracking further comprises:
deleting a cargo unit from a list of the plurality of cargo units when the first member node is deleted from the network, wherein the first member node comprises one of the network capable devices.

### Claim 32 (depends on 28)

The method of claim 28, further comprising:
attaching the network capable devices to the plurality of cargo units.

### Claim 33 (depends on 28)

The method of claim 28, wherein the managing node comprises a hardware network device of a vehicle, and wherein the plurality of cargo units comprise cargo units on board the vehicle.

### Claim 34 (depends on 1)

The method of claim 1, wherein shares of the (k, n1) secret sharing scheme are portions of neither the first key nor the second key.

### Claim 35 (depends on 1)

The method of claim 1, further comprising:
deleting, concurrently, multiple additional ones of the plurality of member nodes using one of a gapped incremental threshold scheme (GITS) and a leaping incremental threshold scheme (LITS).