Trusted Execution Environment (TEE)

Guarantees that code and data inside the TEE cannot be modified by unauthorized entities.

• Mechanism: Cryptographic hashing and Message Authentication Codes (MACs) are computed over memory pages. Any tampering detected during a load operation triggers a fault.
• Protection: Defends against bus snooping and cold boot attacks where an attacker physically alters memory contents.
• Result: The workload either executes correctly or halts entirely—it never produces a result based on corrupted state.

Enforces a strict boundary between the trusted world and the untrusted, rich execution environment.

• Physical Separation: Technologies like ARM TrustZone split the processor into two virtual cores with hardware access controls.
• Enclave Model: Intel SGX and AMD SEV carve out private memory regions that are inaccessible at any privilege level, including ring 0.
• Side-Channel Resistance: Modern TEEs include mitigations against cache-timing and page-fault attacks, though this remains an active area of adversarial research.

Allows a TEE to encrypt data for storage on untrusted media, binding it to a specific enclave identity.

• Seal to Enclave Identity: Data can only be decrypted by the exact same enclave code on the same CPU.
• Seal to Signing Identity: Data can be decrypted by any enclave signed by the same developer key, enabling secure software updates.
• Use Case: Storing long-term secrets, ledger state, or model weights on disk without exposing them to the host file system.

Establishes an unbroken chain of trust from firmware initialization to application execution.

• Process: Each stage of the boot process cryptographically measures the next stage before executing it, storing the hash in Platform Configuration Registers (PCRs).
• Verification: Attestation quotes include these PCR values, allowing a verifier to detect if the BIOS, bootloader, or OS has been compromised.
• Foundation: Without a verified boot chain, the integrity of the TEE itself cannot be guaranteed.

A specific implementation of a TEE that creates an isolated memory region within a process. Code and data inside the enclave are inaccessible to any process outside it, regardless of privilege level.

• Granularity: Protects a specific application component, not the entire VM.
• Attestation: Provides cryptographic proof of the enclave's identity and integrity to a remote party.
• Example: Intel SGX (Software Guard Extensions) is the most widely known enclave technology.

A cryptographic mechanism that allows a TEE to prove its identity, integrity, and that it is running specific code to a remote relying party before that party provisions secrets.

• Process: The TEE generates a hardware-signed quote containing a measurement of its memory.
• Verification: A remote attestation service validates the quote against known good firmware versions.
• Critical for: Establishing trust in multi-party computation and federated learning scenarios.

A cryptographic protocol that enables multiple parties to jointly compute a function over their private inputs while keeping those inputs completely hidden from one another.

• Complement to TEEs: SMPC provides a software-based alternative to hardware trust.
• Trade-off: Offers mathematical privacy guarantees but incurs significant communication overhead compared to the efficiency of TEEs.
• Hybrid Models: Often combined with TEEs for performance-critical secure analytics.

A dedicated physical computing device that safeguards and manages digital keys for strong authentication and provides cryptoprocessing. Unlike a TEE, an HSM is a physically separate processor.

• Function: Secure key generation, storage, and crypto acceleration.
• Form Factor: External appliance or plug-in card.
• Contrast with TEE: TEEs are integrated into the main CPU; HSMs are discrete, tamper-resistant hardware.

A set of unconditionally trusted hardware components that form the foundation for all secure operations in a computing system. The TEE relies on the RoT to establish its integrity.

• Bootstrapping: The RoT is the first piece of code executed at boot, measuring subsequent firmware.
• Immutability: Ideally implemented in immutable ROM or e-fuses.
• Chain of Trust: Extends from the RoT through the bootloader to the TEE and operating system.