About this document

Release information

The change history table lists the changes that have been made to this document.

Table 1 Document revision history





Feb 2019

1.0 beta 2


Initial publication.

June 2019



First stable release with 1.0 API finalized.

Uses the common PSA Certified Status codes.

Modified the API parameters to align with other PSA Certified APIs.

Added storage flags to specify protection requirement.

October 2022



Relicensed as open source under CC BY-SA 4.0.

Documentation clarifications.

March 2023



Documentation clarifications.

January 2024



Provide a Security Risk Assessment.

The detailed changes in each release are described in Document history.

PSA Certified Secure Storage API

Copyright © 2018-2019, 2022-2024 Arm Limited and/or its affiliates. The copyright statement reflects the fact that some draft issues of this document have been released, to a limited circulation.


Text and illustrations

Text and illustrations in this work are licensed under Attribution-ShareAlike 4.0 International (CC BY-SA 4.0). To view a copy of the license, visit creativecommons.org/licenses/by-sa/4.0.

Grant of patent license. Subject to the terms and conditions of this license (both the CC BY-SA 4.0 Public License and this Patent License), each Licensor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section) patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer the Licensed Material, where such license applies only to those patent claims licensable by such Licensor that are necessarily infringed by their contribution(s) alone or by combination of their contribution(s) with the Licensed Material to which such contribution(s) was submitted. If You institute patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that the Licensed Material or a contribution incorporated within the Licensed Material constitutes direct or contributory patent infringement, then any licenses granted to You under this license for that Licensed Material shall terminate as of the date such litigation is filed.

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About the license

The language in the additional patent license is largely identical to that in section 3 of the Apache License, Version 2.0 (Apache 2.0), with two exceptions:

  1. Changes are made related to the defined terms, to align those defined terms with the terminology in CC BY-SA 4.0 rather than Apache 2.0 (for example, changing “Work” to “Licensed Material”).

  2. The scope of the defensive termination clause is changed from “any patent licenses granted to You” to “any licenses granted to You”. This change is intended to help maintain a healthy ecosystem by providing additional protection to the community against patent litigation claims.

To view the full text of the Apache 2.0 license, visit apache.org/licenses/LICENSE-2.0.

Source code

Source code samples in this work are licensed under the Apache License, Version 2.0 (the “License”); you may not use such samples except in compliance with the License. You may obtain a copy of the License at apache.org/licenses/LICENSE-2.0.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

See the License for the specific language governing permissions and limitations under the License.


This document refers to the following documents.

Table 2 Documents referenced by this document


Document Number



ARM DEN 0128

Platform Security Model. developer.arm.com/documentation/den0128


IHI 0086

PSA Certified Crypto API. arm-software.github.io/psa-api/crypto


ARM IHI 0097

PSA Certified Status code API. arm-software.github.io/psa-api/status-code


ARM DEN 0063

Arm® Platform Security Architecture Firmware Framework. developer.arm.com/documentation/den0063


NIST, NIST Special Publication 800-30 Revision 1: Guide for Conducting Risk Assessments, September 2012. doi.org/10.6028/NIST.SP.800-30r1

Terms and abbreviations

This document uses the following terms and abbreviations.

Table 3 Terms and abbreviations



Application Root of Trust (ARoT)

This is the security domain in which additional security services are implemented. See Platform Security Model [PSM].

ARoT See Application Root of Trust.
Implementation Defined

Behavior that is not defined by the this specification, but is defined and documented by individual implementations.

Firmware developers can choose to depend on IMPLEMENTATION DEFINED behavior, but must be aware that their code might not be portable to another implementation.

Non-secure Processing Environment (NSPE)

This is the security domain outside of the Secure Processing Environment. It is the Application domain, typically containing the application firmware and hardware.

NSPE See Non-secure Processing Environment.
Platform Root of Trust (PRoT)

The overall trust anchor for the system. This ensures the platform is securely booted and configured, and establishes the secure environments required to protect security services. See Platform Security Model [PSM].

PRoT See Platform Root of Trust.
Root of Trust (RoT)

This is the minimal set of software, hardware and data that is implicitly trusted in the platform — there is no software or hardware at a deeper level that can verify that the Root of Trust is authentic and unmodified.

Root of Trust Service (RoT Service)

A set of related security operations that are provided by a Root of Trust.

RoT See Root of Trust.
RoT Service See Root of Trust Service.
Secure Partition

A processing context with protected runtime state within the Secure Processing Environment. A secure partition may implement one or more RoT Services, accessible via well-defined interfaces.

Secure Partition Manager (SPM)

Part of the Secure Processing Environment that is responsible for allocating resources to Secure Partitions, managing the isolation and execution of software within partitions, and providing IPC between partitions.

Secure Processing Environment (SPE)

This is the security domain that includes the Platform Root of Trust and the Application Root of Trust domains.

SPE See Secure Processing Environment.
SPM See Secure Partition Manager.

Potential for change

The contents of this specification are stable for version 1.0.

The following may change in updates to the version 1.0 specification:

  • Small optional feature additions.

  • Clarifications.

Significant additions, or any changes that affect the compatibility of the interfaces defined in this specification will only be included in a new major or minor version of the specification.


Typographical conventions

The typographical conventions are:


Introduces special terminology, and denotes citations.


Used for assembler syntax descriptions, pseudocode, and source code examples.

Also used in the main text for instruction mnemonics and for references to other items appearing in assembler syntax descriptions, pseudocode, and source code examples.

small capitals

Used for some common terms such as implementation defined.

Used for a few terms that have specific technical meanings, and are included in the Terms and abbreviations.

Red text

Indicates an open issue.

Blue text

Indicates a link. This can be

  • A cross-reference to another location within the document

  • A URL, for example example.com


Numbers are normally written in decimal. Binary numbers are preceded by 0b, and hexadecimal numbers by 0x.

In both cases, the prefix and the associated value are written in a monospace font, for example 0xFFFF0000. To improve readability, long numbers can be written with an underscore separator between every four characters, for example 0xFFFF_0000_0000_0000. Ignore any underscores when interpreting the value of a number.


We welcome feedback on the PSA Certified API documentation.

If you have comments on the content of this book, visit github.com/arm-software/psa-api/issues to create a new issue at the PSA Certified API GitHub project. Give:

  • The title (Secure Storage API).

  • The number and issue (IHI 0087 1.0.3).

  • The location in the document to which your comments apply.

  • A concise explanation of your comments.

We also welcome general suggestions for additions and improvements.