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What is Trust Onboard

If you received a Twilio Broadband IoT Developer Kit, then check out this tutorial to learn how to set it up and build your first IoT application.


Trust Onboard is a feature where Programmable Wireless SIM cards contain two X.509 certificates. These client-side certificates will be used to authenticate SIM cards in HTTPS connections.

Customers will be able to authenticate with cloud providers such as Microsoft Azure and their own homegrown systems using the TLS handshake.

No additional pre-shared keys (API tokens, passwords, request signing) are needed - only a Twilio SIM card with Trust Onboard. The SIM cards are manufactured with two unique certificates and key pairs with different capabilities, described below.

General use cases

Category Description
Device identity Device identity differentiation at the point of manufacturing, without the installation of custom software or hardware by the device manufacturer
Device protection Software integrity
Secure communication API authentication and authorization

How Trust Onboard starts

  1. Twilio generates a public key, private key, and two certificates (Available Key and Signing Key) per SIM card.
  2. Certificates are loaded on the SIM card during SIM manufacturing.
  3. Twilio provides you with an ICCID to certificate mapping.
  4. Private keys are not stored, other than on the SIM.

SIM certificates onboard

  • Available Key certificates will be on the SIM card but the text is freely available on the device. Your code will have access to the full text of the public and private keys and certificate. This is intended to be used with hardware that requires you to hand over this data for HTTPS communication. These live in a simple global platform applet that holds files with only read operations.
  • Signing Key certificates will be inside the SIM card with no way to export the text contents. You will utilize TLS libraries such as mBed that can request the SIM card to sign requests using the keys and perform request encryption. This is intended for use cases where your hardware allows you to offload the TLS communication to the SIM card. These live in a global platform applet called mIAS that implements a full security suite (similar to OpenSSL).

What is mIAS?

Mobile Identification Authentication Signature applet (mIAS) is a Java Card Applet in a Secure Element, providing functions to integrate with a PKI system:

  • Identification
  • Authentication
  • Signature

SIM certificates lifetime

The SIM certificates have long expiration periods (30 years).

  • Available Key certificates that are able to be extracted out of the SIM onto the device memory can never be replaced. The files (public, private key and certificate) live in a location on the SIM card that is not writable. For this reason the keys are effectively permanent and the certificate should outlive the physical device.
  • Signing Key has the same 30 year expiration period as Available Key.

Sync SIM certificates to your backend

Trust Onboard makes SIM certificates available to you so you can add them to your backend service in order to authenticate connections from your devices. There are couple of ways you can get SIM certificates as shown below.


Sync SIM certificates to your Cloud

With Trust Onboard you can sync your SIM certificates directly with a cloud backend service like Microsoft Azure.

Download SIM certificates

If you have a home grown backend system, then you can download the SIM Certificates and add them to your backend system.

Twilio Certificate bundles

Twilio certificate bundles allow you to verify the authenticity of a SIM certificate. Each bundle file below contains the CA certificates used to sign the certificates on a Twilio SIM card.

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