presidio-deident

De-identify a dataset before you license it to an AI developer, and sign a release record that the buyer verifies offline.

The release record states what was removed, what remained, which opt-out and deletion lists were applied, the sources and rights you declare, and the recipient. It carries counts and hashes and never cell values. The record documents: it never states that the output is anonymous. Whether data is personal for a given recipient is a legal question for you and your counsel.

It runs where the data is. There is no hosted mode and no network access during a run.

Status: alpha (v0.7.0). The record format is dataset-release@1; see docs/SPEC.md and the compatibility rules in SEMVER.md. The requirements and version plan are in PRESIDIO-REQ.md, and decisions in docs/adr/.

Install

pip install presidio-deident        # Python 3.11+; depends on presidio-evidence and cryptography

The buyer installs the same package to verify. PII detection is built in and has no NLP models or other heavy dependencies.

Releaser: five commands

deident inspect tickets.csv                      # columns, missing values, PII types (counts only)
deident policy-init tickets.csv --out policy.toml
#   edit policy.toml: recipient, signer, rights, and review every column's action
deident keygen --signer acme-data-release --sign-key sign.key --pseudonym-key pseudo.key > trust.json
deident run --policy policy.toml --input tickets.csv --out release/ \
            --sign-key sign.key --pseudonym-key pseudo.key
deident verify release/ --trust trust.json       # what the buyer will run

Send the buyer the release/ directory and trust.json, the public key. Never send the keys. Keep the policy file: the record carries its SHA-256.

Buyer: one command

Try it on the signed sample release in this repository (synthetic data):

pip install presidio-deident
git clone https://github.com/presidio-v/presidio-deident && cd presidio-deident
deident verify examples/sample-release --trust examples/sample-trust.json

On a release you received:

deident verify release/ --trust trust.json       # exit 0 only if every check passes
deident verify release/ --trust trust.json --json

Verify checks four things:

• the Ed25519 signature, from a signer in your trust store, bound to the framework dataset-release and to this dataset id (presidio-evidence evidence-ref@3);
• that the signature covers this exact record;
• that the row counts add up;
• that every data file is present, is not a symlink, and matches its SHA-256 and size.

The record says what was done. It does not say the result is anonymised. What it does and does not prove: docs/THREAT-MODEL.md.

Exit codes for every command: 0 verified or done, 1 verification failed, 2 the command could not run. The check names, the --json result (verify-result@1) and the record format are specified in docs/SPEC.md, so a lab can script against them or write its own verifier. Keys and rotation: docs/KEYS.md.

The policy

[release]
dataset_id = "tickets-2026"
recipient = "lab-example"
signer = "acme-data-release"
released_at = "2026-11-08T00:00:00Z"   # optional; fixes the record for a reproducible run

[[release.rights]]
source = "Acme support system export, October 2026"
basis = "Customer terms section 7: licence for AI training"
reference = "contract 2026-114"

[columns]                              # every input column, or the run stops
ticket_id = { action = "pseudonymise" }
email = { action = "drop" }
country = { action = "keep" }
body = { action = "scrub_text" }

[[suppression]]                        # rows whose value is on the list are removed
name = "opt-out-2026-11"
file = "optout.txt"
column = "email"
format = "plain"                       # or "sha256": entries are hex SHA-256 of the normalised value
normalise = ["strip", "lower"]
as_of = "2026-11-01"

California DROP lists. Extract the deletion-list CSVs from the DROP download ZIP and name one per suppression entry with format = "ca-drop" and the matching DROP standardisation:

[[suppression]]
name = "drop-email-2026-11"
file = "20261101_4821_Email.csv"       # header Id,Hash; Hash is SHA-256, Base64
column = "email"
format = "ca-drop"
normalise = ["drop-email"]             # or ["drop-phone"] for the Phone list
as_of = "2026-11-01"

drop-email removes whitespace and lowercases; drop-phone keeps the last 10 ASCII digits. Both are tested against the official CalPrivacy vectors. The composite NDZ and NameVIN lists and the Removed file are not supported yet.

Quasi-identifier risk

Columns that are harmless one by one can single a person out in combination (age, postcode, visit date). Declare them, and the release record carries the equivalence-class distribution of the output, computed after generalisation and suppression:

[risk]
quasi_identifiers = ["age", "postcode", "visit"]
sensitive = ["diagnosis"]       # optional: l-diversity
require_min_k = 5               # optional: stop the run if any class is smaller

The record states the number of classes, the smallest class (min_k), the number of unique rows, the rows by class size, and per sensitive column the smallest number of distinct values in a class (min_l). All of these are integers. It reports the distribution and draws no conclusion from it. deident risk file.csv --qi age,postcode gives the same report for any file, before you write a policy.

Detection is structural and regex-based, vendored from presidio-hardened-x402. It does not find names, addresses or other free-text identifiers. Columns that may hold those should be dropped or reviewed. inspect suggests actions from column names and detected types; the suggestions are a starting point, not a decision.

Re-releases

After the next deletion cycle, release again and name the earlier release as the parent:

deident run --policy policy.toml --input tickets.csv --out release-2026-12/ \
            --sign-key sign.key --pseudonym-key pseudo.key --parent release-2026-11/
deident history release-2026-11/ release-2026-12/ --trust trust.json

The new record lists the earlier record's hash in parents. Pseudonyms stay the same for the same recipient, so the buyer can replace the old rows. history checks the whole chain:

• every release verifies;
• all releases are of one dataset to one recipient;
• there is exactly one root release;
• every parent is in the set and was released earlier.

Add --records-only when the old data files are no longer kept.

Formats

CSV (UTF-8, header required), JSONL (one flat object per line, scalar values) and Parquet (pip install 'presidio-deident[parquet]'). The output keeps the input's format and column order and is byte-for-byte reproducible for the same tool versions.

Parquet columns may be strings, integers, floats, booleans, dates or timestamps. Nested, binary and decimal columns are refused. Kept columns keep their type; columns the policy changes become strings. Dates and timestamps can be generalised.

Roadmap

Full detail is in PRESIDIO-REQ.md.

License

MIT.