The STSAFE-A120 secure element supports the following features:

•

Authentication

The STSAFE-A120 authentication service provides proof to a remote or local host that a certain peripheral

or IoT is legitimate. An equipment manufacturer can thus ensure that only authentic peripherals (like

accessories or consumables) can be used in conjunction with the original equipment. In the same way, a

service provider can make sure that its service only operates with the appropriate IoT device.

The authentication service utilizes the ECC cryptographic scheme with NIST P-256-bit, P-384-bit, P-521-bit

curves, brainpool P-256-bit, P-384-bit, P-512-bit, and curve25519. It is also compliant with various

standards that request object authentication such as CSA Matter, WPC, and OCP M-CRPS.

•

Secure storage

The STSAFE-A120 comes with 16 Kbytes of nonvolatile memory split into areas, whose read and write

access rights can be configured to free access, local host access, or remote host access.

•

Secure one-way counters (peripheral life cycle and usage monitoring)

The STSAFE-A120 offers configurable one-way counters that allow the monitoring of disposable

accessories or consumables. The number of counters available in the user NVM depends on the STSAFE-

A120 personalization.

•

Pairing and secure channel with the host

The STSAFE-A120 allows a secure channel to be set up with the local host based on AES keys for

command authorization, command data encryption, response data encryption, and response

authentication. Typically, pairing between an STSAFE-A120 and its local host prevents the use of the

STSAFE-A120 in a different device and protects the I²C line from eavesdropping of sensitive information.

•

Wrapping and unwrapping local envelopes

The STSAFE-A120 can be used to encrypt or decrypt data with one of its two local envelope keys.

Typically, it can be used when the local host needs to store secrets like connectivity keys and credentials

within its nonsecure data storage area.

•

Secure-channel key establishment (TLS)

The STSAFE-A120 assists the local host in establishing a secure connection between the device and a

remote host (such as a cloud server or gateway). It assists the local host in establishing the session keys

used to encrypt and decrypt data exchanges between the device and the remote host. This key

establishment service relies on the computation of a shared secret based on the elliptic curve Diffie-

Hellman schemes (ECDH and ECDHE) executed after the device has generated and exchanged ECC

NIST, brainpool, or X25519 public keys with the server.

•

Entity authentication

With its public key slots, the STSAFE-A120 can authenticate a local or a remote host. Successful

authentication by the STSAFE-A120 grants the local or remote host access to some authorized

commands, or memory partitions.

•

Signature verification

The STSAFE-A120 can verify an elliptic curve digital signature algorithm (ECDSA) signature by using a

public key provided by the local host. This mechanism can offload a local host application processor with

no or limited cryptographic computing power. It is typically used to verify signatures of firmware in the

context of secure boot or secure firmware update.

•

Symmetric keys

The STSAFE-A120 can be loaded with up to 16 symmetric keys for data encryption and decryption.

•

Data hashing

The STSAFE-A120 allows data hashing with SHA-2 (SHA-256, SHA-384, SHA-512), and SHA-3

(SHA3-256, SHA3-384, SHA3-512) algorithms.

1.2

STSAFE-A120 environment

The STSAFE-A120 comes with a host integration code tested with STMicroelectronics (ST) STM32 general-

purpose MCUs. It can also be ported to a wide range of general-purpose microcontrollers or microprocessors.

This integration code includes a command wrapper and examples for the most common generic use cases.

The STSAFE-A120 is available prepersonalized with generic data profiles for evaluation, prototyping, or

production.

ST also offers and recommends secure provisioning services for key generation and storage of customer leaf

certificates in a secure, certified environment.

The STSAFE-A120 are delivered with an ST CA certificate that allows authenticity verification of the leaf

certificates present in each STSAFE-A120 device.

STSAFE-A120

Description

DS14609 - Rev 1

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