The TEE typically consists of a hardware isolation mechanism, plus a secure operating system running on top of that isolation mechanism – however the term has been used more generally to mean a protected solution.<ref>{{cite book |last1=Sabt |first1=M |title=2015 IEEE Trustcom/BigDataSE/ISPA |pages=57–64 |last2=Achemlal |first2=M |last3=Bouabdallah |first3=A |chapter=Trusted Execution Environment: What It is, and What It is Not |websitepublisher=IEEE |doi=10.1109/Trustcom.2015.357 |year=2015 |isbn=978-1-4673-7952-6 |s2cid=206775888 |url=https://hal.archives-ouvertes.fr/hal-01246364/file/trustcom_2015_tee_what_it_is_what_it_is_not.pdf |access-date=2020-04-19 |archive-date=2020-07-18 |archive-url=https://web.archive.org/web/20200718094655/https://hal.archives-ouvertes.fr/hal-01246364/file/trustcom_2015_tee_what_it_is_what_it_is_not.pdf |url-status=live }}</ref><ref>{{cite journal |last1=Pinto |first1=S. |last2=Santos |first2=N. |date=2019 |title=Demystifying Arm TrustZone: A Comprehensive Survey |url=https://doi.org/10.1145/3291047 |journal=ACM Computing Surveys |volume=51 |pages=1–36 | doi=10.1145/3291047|s2cid=59337370 }}</ref><ref>{{cite journal |last1=Lee |first1=S |last2=Lee |first2=JH |title=TEE based session key establishment protocol for secure infotainment systems |journal=Design Automation for Embedded Systems |volume=22 |issue=3 |pages=215–224 |publisher=Springer |doi=10.1007/s10617-018-9212-5 |year=2018 |s2cid=52081114 }}</ref><ref>{{cite book |last1=Shepherd |first1=C |title=2016 IEEE Trustcom/BigDataSE/ISPA |pages=168–177 |last2=Arfaoui |first2=G |last3=Gurulian |first3=I |last4=Lee |first4=R |last5=Markantonakis |first5=K |last6=Akram |first6=R |last7=Sauveron |first7=D |last8=Conchon |first8=E |chapter=Secure and Trusted Execution: Past, Present, and Future - A Critical Review in the Context of the Internet of Things and Cyber-Physical Systems |websitepublisher=IEEE |doi=10.1109/TrustCom.2016.0060 |year=2016 |isbn=978-1-5090-3205-1 |s2cid=8717045 |url=https://core.ac.uk/download/pdf/77298166.pdf |access-date=2021-05-14 |archive-date=2021-05-14 |archive-url=https://web.archive.org/web/20210514194356/https://core.ac.uk/download/pdf/77298166.pdf |url-status=live }}</ref> Whilst a GlobalPlatform TEE requires hardware isolation, others such as EMVCo use the term TEE to refer to both hardware/software and only software-based solutions.<ref>{{cite web |title=Software-Based Mobile Payment Evaluation Process |url=https://www.emvco.com/processes-forms/product-approval/mobile/sbmp |publisher=EMVCo |access-date=2021-10-13 |archive-date=2021-03-02 |archive-url=https://web.archive.org/web/20210302083210/https://www.emvco.com/processes-forms/product-approval/mobile/sbmp/ |url-status=live }}</ref> FIDO uses the concept of TEE in the restricted operating environment for TEEs based on hardware isolation.<ref>{{cite web |title=FIDO Authenticator Allowed Restricted Operating Environments List |url=https://fidoalliance.org/specs/fido-security-requirements-v1.0-fd-20170524/fido-authenticator-allowed-restricted-operating-environments-list_20170524.html |publisher=FIDO Alliance |access-date=2021-10-13 |archive-date=2021-07-13 |archive-url=https://web.archive.org/web/20210713153906/https://fidoalliance.org/specs/fido-security-requirements-v1.0-fd-20170524/fido-authenticator-allowed-restricted-operating-environments-list_20170524.html |url-status=live }}</ref> Only trusted applications running in a TEE have access to the full power of a device's main processor, peripherals and memory, while hardware isolation protects these from user installed apps running in a main operating system. Software and cryptographic isolation inside the TEE protect the trusted applications contained within from each other.<ref>{{cite web|url=https://www.trustonic.com/products-services/trusted-execution-environment|title=Solutions - Trustonic- Securing Smart Devices & Mobile Applications|website=Trustonic.com|access-date=2014-07-31|archive-date=2014-08-10|archive-url=https://web.archive.org/web/20140810221846/https://www.trustonic.com/products-services/trusted-execution-environment|url-status=live}}</ref>
Service providers, [[mobile network operator]]s (MNO), operating system developers, [[Mobile Application Development|application developers]], device manufacturers, platform providers and silicon vendors are the main stakeholders contributing to the standardization efforts around the TEE.
