Privacy Policy

Last updated: 2026-05-12

paycancel ("the Extension") is operated by UNKRYPT (a sole proprietorship organized in Japan), with Ryohei Mizuno (水野亮平) as its representative (the "Operator"). It is designed with user privacy as the highest priority. This policy explains what information the Extension handles and how. It is written to comply with the EU General Data Protection Regulation (GDPR), the UK Data Protection Act 2018, the California Consumer Privacy Act (as amended by the CPRA), and the Japanese Act on the Protection of Personal Information (APPI).

1. Design Principles

1. No credentials collected. The Extension never receives login IDs, passwords, OAuth tokens, session cookies, or other credentials. All operations occur within the user's own browser session.
2. Local-first by default. Detected subscriptions, cancellation history, screenshots, and browsing-derived data are stored only on the user's device (IndexedDB / chrome.storage.local).
3. End-to-end encryption for cloud sync. When the user opts in to paycancel Encrypted Sync (PES), all data is encrypted on the device with a key derived from the user's passkey (WebAuthn PRF) before transmission. The operator stores only opaque ciphertext and cannot decrypt it.
4. Opt-in for any contribution. Anonymous telemetry, Pioneer Mode contributions, and other forms of community participation require explicit opt-in inside the Extension and can be revoked at any time.
5. No advertising, no cross-site tracking, no cookies.

2. Data Stored Locally on Your Device

The following data is stored within the browser. It is not transmitted to the operator or any third party unless you opt in to specific features (Sections 3–6).

Data	Examples	Storage
Subscription information	service name, amount, currency, cycle, renewal date, payment URL, cancellation URL	IndexedDB
Cancellation history	timestamp, duration, dark patterns encountered, Procedure version	IndexedDB
Cancellation evidence	screenshot (PNG), SHA-256 hash, Ed25519 timestamp signature	IndexedDB
User settings	notification preferences, telemetry consent, reminder days, locale, tier	IndexedDB
Cryptographic keys	Ed25519 keypair for evidence integrity (private key never leaves the device)	chrome.storage.local
Procedure cache	JSON fetched from CDN (public data)	IndexedDB
Pro license token	signed JWT issued by the operator (when applicable)	chrome.storage.local
PES sync state	anonymous user identifier, sync version (no credentials)	chrome.storage.local
PES master secret cache	32-byte AES-256-GCM-encrypted master secret + non-extractable wrapping key	chrome.storage.local (encrypted) + IndexedDB (wrapping key)
Visit history	per-domain visit counts (90-day rolling window, used for unused-subscription detection)	IndexedDB

3. Outbound Network Requests — Default (No Opt-in Required)

Destination	Purpose	Information sent
cdn.paycancel.net/procedures/*	Fetch public Procedure JSON	Service ID only (e.g., "netflix-jp"). No user identifier.
Stripe Checkout / Customer Portal (in a separate browser tab)	Subscription billing (Pro plan only)	Whatever you enter directly into Stripe's pages. The Extension does not see it.
Sentry (only if configured by the operator)	Error monitoring	See Section 6

Personal information, subscription lists, visited URLs, cancellation history, and statistical summaries thereof are never transmitted by default.

4. paycancel Encrypted Sync (PES) — Opt-in End-to-End Encrypted Cloud Sync

If you choose to enable PES, the Extension synchronizes your subscription list, cancellation history, settings, and cancellation evidence across your devices through paycancel's cloud infrastructure. Every byte sent to the cloud is encrypted on your device before transmission.

4.1 Cryptographic design

• Master secret source: a Passkey stored in your operating system's secure enclave (e.g., iCloud Keychain, Google Password Manager, Windows Hello). The Extension never sees the passkey private key. The derived 32-byte master secret is cached on your device after first authentication so you do not need to re-authenticate on every browser session. The cache uses defense-in-depth: the master secret is encrypted (AES-256-GCM) before being written to chrome.storage.local, and the encryption key is a non-extractable Web Crypto key stored in IndexedDB (JavaScript cannot read its raw bytes even via DevTools). The cache lives only on your device, is removed when you disconnect PES or clear all data, and is never transmitted.
• Key derivation: WebAuthn PRF Extension → HKDF-SHA-256 → 256-bit AES key. Different cryptographic contexts use different derived keys.
• Encryption: AES-256-GCM with a fresh random 12-byte IV per record.
• Server visibility: the operator and its sub-processors can see only opaque ciphertext. They cannot decrypt your data even if compelled by legal order.

4.2 What is stored on paycancel infrastructure

Storage	Content	Encrypted?
Supabase user_blobs	Main sync payload (subscriptions, history, settings, license token)	✅ AES-256-GCM
Supabase recovery_codes	SHA-256 hash of a recovery code you generated. Not the recovery code itself.	Hashed
Supabase evidence_blob_refs	Encrypted evidence metadata (blob ID, size, SHA-256 of plaintext, R2 key)	Plaintext metadata only — does not reveal evidence content
Cloudflare R2 paycancel-evidence	Encrypted evidence PNG blobs	✅ AES-256-GCM
Supabase Auth (anonymous user)	Anonymous Supabase user ID derived from passkey credential ID hash	n/a — no email, no name, no phone

The operator does not receive or store: your email, name, phone number, IP address (beyond ephemeral routing necessity), browsing history, or the plaintext contents of any synchronized field.

4.3 Recovery codes — your responsibility

When you set up PES the Extension displays a 52-character recovery code generated entirely on your device. The operator does not retain this code, nor any value from which it can be reconstructed. If you lose access to your passkey AND lose your recovery code, the operator cannot decrypt your synced data. Store the recovery code in a password manager or printed in a safe place.

4.4 Deletion

You may disconnect PES at any time from the Extension's settings. To request server-side deletion of your ciphertext, use the "Disconnect & delete cloud data" UI option or email paycancel.net/#contact with the anonymous user ID shown in the sync panel.

5. Community Authoring & Pioneer Mode — Opt-in Contribution

The Extension's cancellation Procedures are continuously improved through anonymous contributions from users who opt in to Pioneer Mode. This section explains exactly what is shared with the operator when you opt in, and what the operator does with it.

5.1 What is sent when Pioneer Mode is on

When you successfully complete a cancellation on a supported service while Pioneer Mode is enabled, the Extension constructs an observation trace consisting of:

• Service domain only (e.g., netflix.com). URL paths and query parameters are stripped.
• Structural selector signatures — SHA-256 hashes (16-character prefix) of the structural fingerprint of each element you interacted with. The actual DOM, the element text, the element attributes, and any input values are not transmitted.
• Step sequence metadata — event type (click / keypress), order, and timing (with Laplace noise, ε = 1.0, applied).
• Flow signature — a SHA-256 hash that groups identical cancellation flows for k-anonymity bucketing.
• No screenshots, no DOM text, no entered values, no cookies, no URL parameters, no user identifier.

5.2 PII redaction

Before transmission, the trace passes through a regex-based PII filter that drops the entire trace if it detects email addresses, phone numbers, payment-card-like numbers, or UUIDs anywhere in the structural metadata. A second filter at the server boundary provides defense in depth.

5.3 k-Anonymity gating

A community trace is held in a quarantine table on the server. It is only published (as a Procedure candidate) when at least k=3 distinct anonymous contributors have submitted matching flow signatures within a 14-day window and the candidate has not received ≥2 negative quality votes. This makes it structurally impossible for a single user's submission to be visible in the resulting Procedure.

5.4 Operator-Verified Mode

A separately enabled "Operator Mode" is used by paycancel's operator on their own test browser to publish operator-verified Procedures with k=1. This mode is gated by an HMAC secret known only to the operator and is not available to end users.

5.5 Contribution license you grant

When you opt in to Pioneer Mode and your structural traces survive PII filtering and k-anonymity gating, you grant the operator a worldwide, royalty-free, irrevocable, sub-licensable license to use the structural signatures and the resulting derived Procedures for the purpose of operating, improving, and distributing the Extension and its cancellation guidance. This license covers only the anonymized derivatives — not any underlying personal data — because no personal data leaves your device.

5.6 Withdrawal

You can disable Pioneer Mode at any time. Already-submitted traces cannot be individually withdrawn because they are anonymized and bucketed; however, you can request that all traces matching your anonymous contributor ID be purged before publication by writing to paycancel.net/#contact with the contributor ID shown in the Pioneer panel.

6. Anonymous Telemetry & Error Monitoring

6.1 Failure telemetry (opt-in, off by default)

When Settings > Privacy > Contribute anonymous telemetry is enabled, the Extension reports Procedure execution failures with: Procedure ID and version, failed step ID, SHA-256 hash of the surrounding DOM (not the DOM itself), page path with query parameters removed, browser type, and occurrence timestamp. The server enforces k-anonymity (k = 50) before any failure statistic becomes visible to the operator's dashboards. IP addresses are stripped at the server boundary.

6.2 Error monitoring (Sentry)

If error monitoring is enabled in your build, unhandled JavaScript exceptions are sent to Sentry with: error message and stack trace (with chrome-extension://<id>/ origin stripped), Extension version, browser hint, and a randomly-generated event ID. The error reporter explicitly does not include user identifiers, subscription data, page contents, cookies, IP addresses, or URL query parameters.

7. Sub-Processors

Sub-processor	Role	Data they see
Cloudflare, Inc.	CDN, R2 object storage, Pages	Public Procedure JSON; opaque ciphertext blobs
Stripe Payments Europe Ltd. and affiliates	Pro subscription billing	Whatever you enter into Stripe directly
Supabase Inc.	Database, anonymous auth, Edge Functions	Opaque ciphertext for PES; anonymous traces for Community Authoring
Functional Software, Inc. (Sentry)	Error monitoring (only when enabled)	Stack traces and error messages, with origin and IP stripped
Google LLC (Gemini API)	Procedure structural extraction (operator-side pipeline only)	Public Procedure HTML; never user data

8. International Data Transfers

Your encrypted ciphertext and (if you opt in) your anonymous traces may be processed on servers located outside your country of residence. We rely on Standard Contractual Clauses (SCC) and equivalent safeguards in our agreements with sub-processors. Because all user content is end-to-end encrypted before transmission, no party in the data chain (including the operator) can read the plaintext.

9. Data Retention

Data	Retention
Local data (your device)	Until you delete it or uninstall the Extension
PES ciphertext	Until you disconnect or request deletion
Encrypted evidence on R2	Until you delete the corresponding record or disconnect
Anonymous community traces awaiting k-anonymity threshold	14 days from submission; expired traces auto-purged
Aggregated failure statistics	Indefinitely (no PII)
Sentry error events	90 days, then auto-purged by Sentry

10. Your Rights

• Access: all local data is visible in the Extension UI; for server-side data, contact paycancel.net/#contact with your anonymous user ID.
• Delete: Settings → Data Management → "Delete all data" (local); PES disconnect (server).
• Export: your cancellation history as an HTML certificate.
• Withdraw consent: telemetry, Pioneer Mode, and PES at any time.

EU / UK Residents (GDPR, UK GDPR)

• Legal bases: contract performance (core functionality), explicit consent (telemetry, Pioneer Mode, PES), legitimate interest (security / error monitoring with stripped IPs).
• Data Controller: UNKRYPT (Representative: Ryohei Mizuno), operating under the trade name "paycancel". Contact: paycancel.net/#contact.
• Right to lodge a complaint with your local Data Protection Authority.
• Right to data portability: see "Export" above.
• Automated decision-making: none.

California Residents (CCPA / CPRA)

• We do not "sell" or "share" personal information as those terms are defined by the CCPA / CPRA.
• We do not engage in cross-context behavioral advertising.
• We do not knowingly collect or sell personal information of minors under 16.
• Submit verifiable consumer requests via paycancel.net/#contact. Response within 45 days.

Japan Residents (APPI)

• 個人情報取扱事業者: UNKRYPT（代表: 水野亮平、屋号 paycancel）。Contact: paycancel.net/#contact.
• We do not provide personal data to third parties except as listed in Section 7, as required by law, or with your consent.

Children

The Extension is not intended for children under 13 (16 in the EU). We do not knowingly collect personal information from such users.

11. Security

We use industry-standard encryption (AES-256-GCM, HKDF-SHA-256, Ed25519, WebAuthn) and host on infrastructure that holds SOC 2 certification (Cloudflare, Supabase). No system is perfectly secure, and the security of data on your own device depends on your operating system and account hygiene. If a security incident affects your data, we will notify you within 72 hours of becoming aware, in accordance with GDPR Article 33.

12. Changes to This Policy

We will notify you of material changes via the Extension UI before they take effect. For changes that would reduce your existing rights, we will request explicit re-consent. The "Last updated" date is authoritative.

13. Contact

• Privacy inquiries: paycancel.net/#contact
• General support: support@paycancel.net
• Postal address: provided upon written request to paycancel.net/#contact

14. Governing Law

For users residing in Japan, this policy is governed by Japanese law. For other users, the mandatory data-protection laws of your country of residence apply; in their absence, the law of England and Wales applies.