TLS/SSL for encrypted communication in IOT Protocols - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of OpenSSL command to check certificate expiration

What is the output of this command when run on a valid certificate file named device.crt?

openssl x509 -enddate -noout -in device.crt

IOT Protocols

openssl x509 -enddate -noout -in device.crt

A notAfter=Jun 30 23:59:59 2025 GMT

B Error: unable to load certificate

C Certificate expires on 2025-06-30

D notBefore=Jun 30 23:59:59 2025 GMT

💡 Hint

The command shows the expiration date of the certificate with a 'notAfter' prefix.

The -enddate option outputs the expiration date prefixed by 'notAfter'. Other options or errors indicate wrong command usage or invalid files.

🧠 Conceptual

intermediate

Purpose of TLS Handshake in IoT devices

What is the main purpose of the TLS handshake process in encrypted communication for IoT devices?

A To update the device firmware automatically

B To send data packets faster by skipping encryption

C To compress data before transmission

D To establish a secure connection by agreeing on encryption keys and verifying identities

💡 Hint

Think about what needs to happen before encrypted data can be safely sent.

The TLS handshake sets up encryption keys and verifies the communicating parties to ensure secure data exchange.

❓ Troubleshoot

advanced

Troubleshooting TLS connection failure due to certificate mismatch

An IoT device fails to connect securely to a server using TLS. The error log shows: certificate verify failed: hostname mismatch. What is the most likely cause?

A The TLS version used is outdated

B The device's clock is set to a future date

C The server's certificate common name does not match the server hostname the device is connecting to

D The device's private key is missing

💡 Hint

Hostname mismatch means the name on the certificate does not match the address used.

TLS verifies that the server's certificate matches the hostname the client connects to. A mismatch causes verification failure.

🔀 Workflow

advanced

Correct order of steps in TLS handshake for IoT device connection

Arrange the following steps in the correct order during a TLS handshake between an IoT device and a server.

A 1,2,3,4

B 2,1,3,4

C 1,3,2,4

D 3,1,2,4

💡 Hint

The client starts the handshake, then the server responds, then certificate exchange happens.

The handshake begins with ClientHello, followed by ServerHello, then certificate exchange, and finally client key exchange.

✅ Best Practice

expert

Best practice for securing IoT device TLS private keys

Which of the following is the best practice to protect the private keys used by IoT devices for TLS encrypted communication?

A Embed private keys directly in the device firmware as plain text

B Store private keys in a hardware secure element or trusted platform module (TPM)

C Share private keys among multiple devices to simplify management

D Use the same private key for all devices to reduce complexity

💡 Hint

Think about how to keep keys safe from theft or tampering.

Hardware secure elements or TPMs protect private keys from extraction and unauthorized use, improving security.