# US 7,609,838 B2 · Method of transmitting data in a network

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- Number: US 7,609,838 B2
- Document ID: US7609838B2
- Status: Granted
- Kind: B2
- Application number: 11/094,394
- Filed: 2005-03-31
- Published: 2005-10-06
- Granted: 2009-10-27
- Earliest claimed: 2004-03-31
- Assignees: NEC Corporation
- Inventors: Dirk Westhoff; Joao Girao
- Web page: https://patentgrep.com/patent/US7609838B2

## CPC

- H04L 9/008: {involving homomorphic encryption}
- H04L 2209/805: Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Method to transmit data in an ad hoc network or a sensor network with the network comprising a multitude of sensor nodes to sensor data, at least one aggregator node to aggregate the sensored data of at least a subset of the sensor nodes, and at least one sink node to collect the data of the aggregator node is characterized in—regarding a high level of security against attacks from outside while transmitting data, and regarding an economic energy consumption—that the sensored data is encrypted at the sensor nodes, that the encrypted data is transmitted to one of the aggregator nodes, that at the aggregator node an aggregation function is executed on the encrypted data, and that the result of the aggregation function is transmitted to the sink node and decrypted there.

## Claims

### Claim 1

A method for transmitting data in a network, wherein the network comprises a plurality of sensor nodes to sensor data, at least one aggregator node to aggregate sensored data obtained by at least a subset of the sensor nodes, and at least one sink node to collect data aggregated by the aggregator nodes, the method comprising:
at each of the sensor nodes,
encrypting the sensored data;
transmitting the encrypted data to one of the aggregator nodes;
at the aggregator node,
executing an aggregation function on the encrypted data;
transmitting the result of the aggregation function to the sink node; and
at the sink node,
decrypting the result of the aggregation function.

### Claim 2 (depends on 1)

The method according to claim 1, wherein an encryption transformation is selected in such a way that when applied to the aggregation function the result of the decryption matches the result of the aggregation function if executed on the unencrypted data of the respective sensor nodes.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the encryption transformation is selected from the class of privacy homomorphisms.

### Claim 4 (depends on 3)

The method according to claim 3, wherein an addition, a subtraction, a multiplication or an inverse multiplication is performed by the aggregation function.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the aggregation function is used to represent a computation of an average.

### Claim 6 (depends on 4)

The method according to claim 4, wherein the aggregation function is used to represent a detection of a movement.

### Claim 7 (depends on 1)

The method according to claim 1, wherein the sink node transmits a request to the sensor nodes at predetermined intervals.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the network is an ad hoc network.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the network is a sensor network.

### Claim 10

A system for transmitting data in a network, wherein the network comprises a plurality of sensor nodes to sensor data, at least one aggregator node to aggregate sensored data obtained by at least a subset of the sensor nodes, and at least one sink node to collect data aggregated by the aggregator nodes, wherein
each of the sensor nodes encrypts the sensored data and transmits the encrypted data to one of the aggregator nodes;
the aggregator node executes an aggregation function on the encrypted data, and transmits the result of the aggregation function to the sink node; and
the sink node decrypts the result of the aggregation function.

### Claim 11 (depends on 1)

The method according to claim 1, wherein the aggregator node and the sink node are separate physical nodes.

### Claim 12 (depends on 10)

The system for transmitting data in a network according to claim 10, wherein the aggregator node and the sink node are separate physical nodes.