STSAFE-A110 datasheet(10/36 Pages) STMICROELECTRONICS

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Asymmetric cryptography use cases

STSAFE-A110

10/36

DS13039 Rev 1

Asymmetric cryptography use cases

This chapter illustrates the many uses of an STSAFE-A110 device using asymmetric

cryptography.

2.1

Authentication

This scenario illustrates the command flow where the STSAFE-A110 is mounted on a

device that authenticates to a remote host (IoT device case), the local host being used as a

pass-through to the remote server.

The scenario where the STSAFE-A110 is mounted on a peripheral that authenticates to a

local host, for example games, mobile accessories or consumables, is exactly the same.

Command flow (see Figure 5)

Obtain the public key of the STSAFE-A110 chip in the host device:

–

Command 1 is used to read the X509 public key certificate from the data partition

of the STSAFE-A110 chip.

–

The host device verifies the X509 public key certificate with the CA public key (the

host is responsible for getting a copy of this key). When the verification process

succeeds, the host device has an authentic copy of the STSAFE-A110 public key

that it will use later on for verification of the signature.

The host device generates a challenge and stores it for later use in the verification of

the signature. The host device then computes a hash of this challenge and sends it to

the STSAFE-A110 in Command 2 in order to fetch the signature that the STSAFE-A110

chip computed with its private key. The host device verifies the signature with the

STSAFE-A110 public key (obtained in the first step of this scenario). When valid, the

host knows that the peripheral or IoT is authentic.

Figure 5. Example of peripheral or IoT device authentication

STSAFE-A110 Datasheet(PDF) 10 Page - STMicroelectronics