What three emerging techniques aim to protect data while it is in use (being computed on)?

Secure Multi-Party Computation (MPC), Confidential Computing (TEEs), and Homomorphic Encryption (HE).

Each attacks the data-in-use problem from a different angle:

• MPC — split the computation across parties so no single party ever sees the whole input ("analyze a shared database you can't see").
• Confidential Computing — compute inside a hardware-protected enclave so even the OS/cloud host can't peek ("a secure vault inside the processor").
• Homomorphic Encryption — compute directly on ciphertext, so the data is never decrypted at all.

Tip: These are the headline Privacy-Enhancing Technologies (PETs) for computation. They're not mutually exclusive — they can be layered.