# US 12,113,909 B2 · Method and electronic device for decrypting homomorphically encrypted data

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- Number: US 12,113,909 B2
- Document ID: US12113909B2
- Status: Granted
- Kind: B2
- Application number: 17/661,056
- Filed: 2022-04-28
- Published: 2023-11-02
- Granted: 2024-10-08
- Earliest claimed: 2022-04-28
- Assignees: NXP B.V.
- Applicants: NXP B.V.
- Inventors: Adrian Marotzke; Leonard Clemens Püttjer
- Web page: https://patentgrep.com/patent/US12113909B2

## CPC

- H04L 9/3242: {involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC}
- H04L 9/008: {involving homomorphic encryption}
- H04L 9/0643: {Hash functions, e.g. MD5, SHA, HMAC or f9 MAC}
- H04L 9/085: {Secret sharing or secret splitting, e.g. threshold schemes}
- H04L 9/0894: {Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage}
- H04L 9/3213: {using tickets or tokens, e.g. Kerberos (network architectures or network communication protocols for entities authentication using tickets in a packet data network H04L63/0807)}
- H04L 9/3228: {One-time or temporary data, i.e. information which is sent for every authentication or authorization, e.g. one-time-password, one-time-token or one-time-key}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A method and electronic device are provided for decrypting homomorphically encrypted (HE) data. The method may include generating, in the electronic device, result metadata that specifies a size of the HE data to be decrypted. The electronic device generates or collects HE input data and the result metadata. The HE input data and the encrypted result metadata are transmitted to a cloud server in a cloud environment to allow the cloud server to perform computations using the HE input data. The cloud server is enabled by the hardware device to send a result of the computations on the HE input data to a secure element (SE) for decryption. A relatively secure online connection is established to the SE in the cloud environment. The SE is enabled by the electronic device to decrypt the result of the computations on the HE input data as specified by the result metadata.

## Claims

### Claim 1

A method comprising:
generating, in an electronic device, result metadata, wherein the result metadata specifies a size of homomorphically encrypted (HE) data to be decrypted;
encrypting the result metadata;
generating or collecting, by the electronic device, HE input data;
transmitting the HE input data and the encrypted result metadata to a cloud server in a cloud environment to allow the cloud server to perform computations using the HE input data, and wherein the cloud server is enabled by the electronic device to send a result of the computations on the HE input data to a secure element for decryption;
establishing a relatively secure online connection from the electronic device to the secure element in the cloud environment; and
enabling, by the electronic device, the secure element to decrypt the result metadata and to decrypt the result of the computations on the HE input data as specified by the decrypted result metadata.

### Claim 2 (depends on 1)

The method of claim 1, wherein the electronic device is an edge device for an internet of things system.

### Claim 3 (depends on 1)

The method of claim 1, wherein the secure element decrypts the result of the computations on the HE input data using a keyed-hash message authentication code (HMAC) one time password (HOTP) token.

### Claim 4 (depends on 3)

The method of claim 3, wherein the electronic device generates the HOTP token by hashing a shared secret, the encrypted result metadata, and a current counter value.

### Claim 5 (depends on 3)

The method of claim 3, wherein generating the HOTP token includes incrementing a counter value by 1 after the HOTP token is generated.

### Claim 6 (depends on 1)

The method of claim 1, further comprising synchronizing an HE key, a shared secret, and a counter value between the secure element and the electronic device to further enable the secure element to decrypt the result of the computations on the HE input data.

### Claim 7 (depends on 6)

The method of claim 6, wherein the result metadata is encrypted using a symmetric authenticated encryption scheme.

### Claim 8 (depends on 1)

The method of claim 1, wherein after the secure element decrypts the result of the computations on the HE input data, the decrypted result of the computations is sent to the cloud server.

### Claim 9 (depends on 1)

The method of claim 1, wherein the secure element is implemented as part of the cloud server.

### Claim 10 (depends on 1)

The method of claim 1, wherein the computations on the HE input data are performed using a machine learning model.

### Claim 11

A method comprising:
generating, in an electronic device, result metadata and a keyed-hash message authentication code (HMAC) one time password (HOTP) token, wherein the result metadata specifies a size of homomorphically encrypted (HE) data to be decrypted;
encrypting the result metadata with a metadata key;
generating or collecting, by the electronic device, HE input data;
transmitting the HE input data, the encrypted result metadata, and the HOTP token to a cloud server in a cloud environment to allow the cloud server to perform computations using the HE input data, and wherein the cloud server is enabled by the electronic device to send a result of the computations on the HE input data to a secure element for decryption;
establishing a relatively secure online connection to the secure element in the cloud environment; and
synchronizing a HE key, a shared secret, and a counter value between the secure element and the electronic device to enable the secure element to decrypt the result metadata and to decrypt the result of the computations on the HE input data as specified by the decrypted result metadata.

### Claim 12 (depends on 11)

The method of claim 11, wherein the secure element is enabled by the electronic device to generate an output hash using the shared secret, the result metadata, and a current counter value, wherein the secure element is enabled by the electronic device to compare the output hash to the HOTP token, and wherein if the output hash is identical to the HOTP token, the result of the computations on the HE input data is decrypted, and if the output hash is not identical to the HOTP token, the secure element does not decrypt the result of the computations on the HE data.

### Claim 13 (depends on 12)

The method of claim 12, wherein the current counter value is incremented by one after the result of the computations on the HE input data is decrypted.

### Claim 14 (depends on 12)

The method of claim 12, wherein the decrypted result of the computations on the HE input data is provided to the cloud server.

### Claim 15 (depends on 11)

The method of claim 11, wherein the result metadata is encrypted using a symmetric authenticated encryption scheme.

### Claim 16 (depends on 11)

The method of claim 11, wherein the size of the HE input data to be decrypted as specified by the result metadata is selectable.

### Claim 17

An electronic device comprising:
a processor for generating encrypted result metadata, wherein the encrypted result metadata specifies a size of a homomorphically encrypted (HE) data to be decrypted;
a data generator for generating HE input data; and
a network interface for controlling transmission of the HE input data and the encrypted result metadata to a cloud server in a cloud environment,
wherein the electronic device enables the cloud server to perform computations using the HE input data, and wherein the cloud server is enabled by the electronic device to send a result of the computations using the HE input data to a secure element in the cloud environment for decryption, and
wherein the electronic device enables the secure element to decrypt the result of the computations using the HE input data according to the size specified by the result metadata.

### Claim 18 (depends on 17)

The electronic device of claim 17, wherein the secure element decrypts the result of the computations on the HE input data using a keyed-hash message authentication code (HMAC) one time password (HOTP) token.

### Claim 19 (depends on 18)

The electronic device of claim 18, wherein the electronic device generates the HOTP token by hashing a shared secret, the encrypted results metadata, and a current counter value.

### Claim 20 (depends on 17)

The electronic device of claim 17, wherein the result of the computations on the HE input data is generated by a machine learning model.