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Documentation > Security > MQTT Transport > X.509 Certificate based authentication
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X.509 Certificate Based Authentication

X.509 Certificates are used to setup mutual (two-way) authentication for MQTT over TLS. It is similar to access token authentication, but uses X.509 Certificate instead of token.

Instructions below will describe how to connect MQTT client using X.509 Certificate to ThingsBoard Cloud.

Step 1. Download Server certificate chain

The client device verifies the identity of a server using server certificate. ThingsBoard Cloud uses a valid certificate. Please download the certificate chain using this link and save it to your working directory as β€œtb-cloud-chain.pem”.

Step 2. Generate Client certificate

Use the following command to generate the self-signed private key and x509 certificate. The command is based on the openssl tool which is most likely already installed on your workstation:

To generate the RSA based key and certificate, use:

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openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -sha256 -days 365 -nodes

To generate the EC based key and certificate, use:

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openssl ecparam -out key.pem -name secp256r1 -genkey
openssl req -new -key key.pem -x509 -nodes -days 365 -out cert.pem 

The output of the command will be a private key file key.pem and a public certificate cert.pem. We will use them in next steps.

Step 3. Provision Client Public Key as Device Credentials

Go to ThingsBoard Web UI -> Device Groups -> Group β€œAll” -> Your Device -> Device Credentials. Select X.509 Certificate device credentials, insert the contents of cert.pem file and click save. Alternatively, the same can be done through the REST API.

Step 4. Test the connection

Execute the following command to upload temperature readings to ThingsBoard Cloud using secure channel:

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mosquitto_pub --cafile tb-cloud-chain.pem -d -q 1 -h "mqtt.thingsboard.cloud" -p "8883" \
-t "v1/devices/me/telemetry" --key key.pem --cert cert.pem -m {"temperature":25}