A cloud team must let a downstream analytics service keep processing customer card numbers in the same fixed length and character layout, while ensuring the stored values can be swapped back to the originals only by an authorised service holding a mapping. Which technique meets this requirement?
- ATokenisation that replaces each card number with a surrogate of the same length and format, resolvable only through a protected token vault Correct
- BFormat-preserving encryption applied with a shared symmetric key printed in the application configuration
- COne-way salted hashing of each card number before it is written to the analytics store
- DStatic data masking that overwrites the middle digits with a fixed character while leaving the last four visible
Why A is correct: Tokenisation substitutes a format-matching surrogate that carries no mathematical relationship to the original, and only the vault holding the mapping can reverse it, satisfying both the format and controlled-reversal requirements.
Why B is wrong: Format-preserving encryption does keep the layout and is reversible, but storing the key in plaintext application config defeats the protection, so this is the weaker choice the requirement does not describe.
Why C is wrong: Hashing preserves neither the format in a useful way nor reversibility, so the originals could never be recovered, which contradicts the stated need to swap values back.
Why D is wrong: Masking is deliberately irreversible for the masked characters, so although it preserves the display format it cannot be swapped back to the original value as required.