# Data encryption
<a name="data-encryption"></a>

AWS IoT Greengrass uses encryption to protect data while in-transit (over the internet or local network) and at rest (stored in the AWS Cloud).

Devices in a AWS IoT Greengrass environment often collect data that's sent to AWS services for further processing. For more information about data encryption on other AWS services, see the security documentation for that service.

**Topics**
+ [Encryption in transit](encryption-in-transit.md)
+ [Encryption at rest](encryption-at-rest.md)
+ [Key management for the Greengrass core device](key-management.md)

# Encryption in transit
<a name="encryption-in-transit"></a>

AWS IoT Greengrass has two modes of communication where data is in transit:
+ [Data in transit over the internet](#data-in-transit-internet). Communication between a Greengrass core and AWS IoT Greengrass over the internet is encrypted.
+ [Data on the core device](#data-in-transit-locally). Communication between components on the Greengrass core device is not encrypted.

## Data in transit over the internet
<a name="data-in-transit-internet"></a>

AWS IoT Greengrass uses Transport Layer Security (TLS) to encrypt all communication over the internet. All data sent to the AWS Cloud is sent over a TLS connection using MQTT or HTTPS protocols, so it is secure by default. AWS IoT Greengrass uses the AWS IoT transport security model. For more information, see [Transport security](https://docs.aws.amazon.com/iot/latest/developerguide/transport-security.html) in the *AWS IoT Core Developer Guide*.

## Data on the core device
<a name="data-in-transit-locally"></a>

AWS IoT Greengrass doesn't encrypt data exchanged locally on the Greengrass core device because the data doesn't leave the device. This includes communication between user-defined components, the AWS IoT device SDK, and public components, such as stream manager.

# Encryption at rest
<a name="encryption-at-rest"></a>

AWS IoT Greengrass stores your data:
+ [Data at rest in the AWS Cloud](#data-at-rest-cloud). This data is encrypted.
+ [Data at rest on the Greengrass core](#data-at-rest-device). This data is not encrypted (except local copies of your secrets).

## Data at rest in the AWS Cloud
<a name="data-at-rest-cloud"></a>

AWS IoT Greengrass encrypts customer data stored in the AWS Cloud. This data is protected using AWS KMS keys that are managed by AWS IoT Greengrass.

## Data at rest on the Greengrass core
<a name="data-at-rest-device"></a>

AWS IoT Greengrass relies on Unix file permissions and full-disk encryption (if enabled) to protect data at rest on the core. It is your responsibility to secure the file system and device.

However, AWS IoT Greengrass does encrypt local copies of your secrets retrieved from AWS Secrets Manager. For more information, see the [secret manager](secret-manager-component.md) component.

# Key management for the Greengrass core device
<a name="key-management"></a>

It's the responsibility of the customer to guarantee secure storage of cryptographic (public and private) keys on the Greengrass core device. AWS IoT Greengrass uses public and private keys for the following scenario:
+ The IoT client key is used with the IoT certificate to authenticate the Transport Layer Security (TLS) handshake when a Greengrass core connects to AWS IoT Core. For more information, see [Device authentication and authorization for AWS IoT Greengrass](device-auth.md).
**Note**  
The key and certificate are also referred to as the core private key and the core device certificate.

A Greengrass core device supports private key storage using file system permissions or a [hardware security module](hardware-security.md). If you use file system-based private keys, you are responsible for their secure storage on the core device.