When would you use symmetric encryption versus tokenization for pseudonymization?

Use symmetric encryption when you need to restore the original value; use tokenization when you want random stand-ins with no mathematical link to the data.

• Symmetric encryption (e.g. AES-256): a reversible transformation. Anyone with the key recovers the original. Use it when linkage or restoration is needed. The risk is entirely in key management — key loss = data loss; key theft = full exposure.
• Tokenization: sensitive values are swapped for random tokens, with the real values held in a separate secure vault. The token has no mathematical relationship to the original, so even a leaked token reveals nothing without vault access. It's the standard in PCI / finance (e.g. replacing card numbers).

The trade-off: encryption is portable but the secret travels with the ciphertext's recoverability; tokenization centralizes the secret in a vault, shrinking the attack surface in the dataset itself.

Tip: Encryption transforms the value; tokenization replaces it with an unrelated stand-in. Choose based on whether you ever need the original back, and where you'd rather concentrate risk.

Go deeper:

• Tokenization (data security) (Wikipedia) — random stand-ins + vault, PCI use.
• Data masking (Wikipedia) — situates encryption/tokenization among masking techniques.