ESP8266-PubSubClient-Secure

On the Internet, there are many examples of implementing secure connections for MQTT, but they are all outdated.

I took the liberty of writing a few examples for modern libraries.

• ESP8266 Arduino core ver 2.5.0
• PubSubClient ver 2.7
• ArduinoJson ver 6.10.0

Generate Certificates

I suggest to generate certificates by myself using the openssl utility. You can also use other certificates.

First of all, we need to generate a self-signed CA certificate.

Generate Key for CA:

openssl genrsa -out rootCA.key 2048

Generate self-signed CA Certificate:

openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 1024 -out rootCA.pem

Now we generate a certificate for the client, i.e. of our device.

Note: for each device you need to generate a separate key-certificate pair and sign them with a CA certificate

Generate private key for the client:

openssl genrsa -out client.key 2048

Request for Certificate Signing Request (CSR) to generate client certificate:

openssl req -new -key client.key -out client.csr

Generate Client Certificate:

openssl x509 -req -in client.csr -CA rootCA.pem -CAkey rootCA.key -CAcreateserial -out client.pem -days 500 -sha256