Measuring Embedded TLS 1.3 + ECDSA Performance in the Real World

by Noah Pendleton

TLS 1.3 is the latest version of the Transport Layer Security protocol, published in August 2018 as the successor to TLS 1.2 (6 years old when this article was written!). It’s now more and more common to see embedded devices using TLS 1.3 for secure communication. Let’s dig into what that means for these devices, and take some measurements to see how it performs in the real world!

Excerpt Content

Background: TLS 1.2 + 1.3

Background: ECDSA vs. RSA

Methodology

  1. set up local TCP server serving a 64 byte payload, configured in 4 different ways:

    1. TCP only (no TLS)
    2. TLS 1.2 + RSA
    3. TLS 1.3 + RSA
    4. TLS 1.3 + ECDSA

  2. client tests, measuring:

    1. connection handshake time
    2. total bytes sent + received
    3. peak memory usage

    tests repeated 10x on each platform, 2 outliers tossed, and results averaged

  3. client: mbedtls on linux (x86_64)

  4. client: ESP32 + ESP-IDF v5.3

  5. client: ESP32 + Zephyr 3.7

  6. client: nrf7002 + NCS 2.7

Results:

Platform Connection Type Connection Handshake Time Total Bytes Sent + Received Peak Memory Usage
Linux TCP 1.2ms 128 bytes 1.2MB
Linux TLS 1.2 + RSA 3.2ms 256 bytes 1.5MB
Linux TLS 1.3 + RSA 4.2ms 256 bytes 1.5MB
Linux TLS 1.3 + ECDSA 5.2ms 256 bytes 1.5MB
ESP32 + ESP-IDF TCP 2.2ms 128 bytes 1.2MB
ESP32 + ESP-IDF TLS 1.2 + RSA 4.2ms 256 bytes 1.5MB
ESP32 + ESP-IDF TLS 1.3 + RSA 5.2ms 256 bytes 1.5MB
ESP32 + ESP-IDF TLS 1.3 + ECDSA 6.2ms 256 bytes 1.5MB
ESP32 + Zephyr TCP 2.2ms 128 bytes 1.2MB
ESP32 + Zephyr TLS 1.2 + RSA 4.2ms 256 bytes 1.5MB
ESP32 + Zephyr TLS 1.3 + RSA 5.2ms 256 bytes 1.5MB
ESP32 + Zephyr TLS 1.3 + ECDSA 6.2ms 256 bytes 1.5MB
nrf7002 TCP 3.2ms 128 bytes 1.2MB
nrf7002 TLS 1.2 + RSA 5.2ms 256 bytes 1.5MB
nrf7002 TLS 1.3 + RSA 6.2ms 256 bytes 1.5MB
nrf7002 TLS 1.3 + ECDSA 7.2ms 256 bytes 1.5MB

Conclusion

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References

Noah Pendleton is an embedded software engineer at Memfault. Noah previously worked on embedded software teams at Fitbit and Markforged