問題文
An engineer wants to detect duplicate records without storing email addresses in a matching table. Which use of hashing is sound, and what limitation remains?
選択肢
- Store a keyed hash of the address so that duplicates match, but note that the value still identifies the same person and remains personal data.
- Store the hash with a random salt per record, because that prevents the values from being compared.
- Store some encrypted form of the address, because encryption also produces a fixed-length value.
- Store an unkeyed hash of the address, because a one-way function cannot be reversed and the digest therefore contains no personal data.