1 · Copybook
2 · Data
3 · Key
Use one key for files that must still match each other after masking. A typed key should be long and kept private, never sent with the masked file: anyone with the key and a guess of a real value can check that guess. Masked values can repeat by chance, and masking replaces values; it does not by itself make a file anonymous.
4 · Fields to mask
Paste a copybook first, or load the example.
ACCURACY · CHECKED AGAINST IBM RULES
Masks byte by byte with the copybook layout, so record lengths and unmasked bytes are unchanged and masked numbers stay valid; covered by tests. It replaces values, it does not certify a file as anonymous: free text, keys and unmarked fields can still identify people, so follow your organisation's data rules.
Suggest a tool or report a wrong answer · How it works and why it is safe