KAI-Pay
Wallet

Terms of use

These terms apply to KAI-Pay, a self-custodial Bitcoin and Lightning wallet without a user account, in the browser and as an Android app, and to the point of sale and the payment-link pages. KAI-Pay is a public beta. Please also read the risk warnings and the privacy policy.

1. Contracting party and scope

Your contracting party is exclusively Formsys GmbH. These terms govern use of the KAI-Pay software it supplies, in the version currently provided; the version is shown in the app under “Settings” → “About”. Full provider details are set out in the legal notice.

Shareholders, managing directors, employees, developers and authors of KAI-Pay do not themselves become parties to the contract and give no personal guarantees, warranties or undertakings to answer for obligations. Statutory claims that exist against them independently of these terms remain unaffected, subject to section 12.

KAI-Pay comprises:

These terms apply to adult natural persons and duly represented businesses. These terms do not govern purchases from merchants or separate services supplied by an identified third party. Individual agreements and mandatory statutory rights remain unaffected.

2. Free of charge, no order, no payment obligation

There is no ordering process and no user account is required: the wallet is created on your device. We provide KAI-Pay free of charge: we charge nothing for using it and do not use your data as consideration, for example for advertising. Opening or installing the app alone does not create a payment obligation. Third-party fees for individual payments are described in section 6.

Separately, an Oracle timestamp ordered from the wallet (the “Timestamp” button for registered companies) is a separate service supplied by Formsys GmbH under the product name KAI Oracle, not a Strike service. It is not part of the free wallet; the service description, price and terms applicable to your access that are shown before ordering apply to it. The wallet computes the file digest (SHA-256) on the device and sends the digest, not the document, to KAI Oracle as part of that specific order (privacy policy 2.21).

3. Scope of the beta

KAI-Pay currently offers:

Not offered are buying or selling bitcoin by us, including accepting or forwarding purchase orders (for the link to an external purchase provider see section 15), exchanging into other crypto-assets or tokens, Lightning channels of our own, and holding funds on your behalf. Which features an Android test version contains depends on its version.

The Breez SDK is part of our software as a program library. KAI-Pay also depends on services of other providers that you use directly through the app: Breez’s services (including breez.tips), the Spark operators, the Spark service provider Lightspark, Cloudflare for delivery and servers, and other services named in the privacy policy. These providers supply their services themselves; they are not part of our service, and we do not promise their availability. Our responsibility for our own breaches of duty, for example in selecting and integrating these services, remains under section 12.

As a beta, KAI-Pay is under continuous development. We may change, restrict or discontinue individual features if a provider under the previous paragraph changes or discontinues its service, if this is necessary to fix a security vulnerability or a bug, if statutory or regulatory requirements demand it, or if we develop a feature further and it remains equivalent; in each case only to the extent the change is reasonable for you and at no extra cost to you. We inform you in advance about adverse changes (section 10). Access to your balance via your 12 words does not depend on individual features of the app, but it does depend on the cooperation of the Spark operators (section 4). We promise no particular or uninterrupted availability, no absolute security and no recovery that succeeds in every case. Our duty to provide the software with due care remains unaffected.

4. Self-custody and access

KAI-Pay operates exclusively in self-custody mode. Wallet keys are generated on your device under your control or imported from your recovery words; for a passkey wallet they are derived from your passkey. Formsys GmbH does not receive your keys, has no access to your balance, does not hold a copy enabling it to dispose of your BTC and does not maintain a withdrawable customer balance. This presupposes that the app works as we deliver it; the delivery of the app code is therefore a trust anchor (privacy policy and “Who sees what?”). We therefore can neither freeze nor move your balance, cannot claw back completed payments and cannot refund amounts from your wallet. We cannot replace lost keys or words. Legal claims against us remain unaffected.

KAI-Pay uses the Breez SDK and the Spark network. Payments via Spark require the cooperation of the Spark operators; we are not a Spark operator. A local confirmation does not mean that payment runs exclusively on the device. With the software, Formsys GmbH provides no bank account and promises neither deposit protection nor payouts that are free of disruption at all times. Without that cooperation, the Spark protocol provides for a unilateral exit to the Bitcoin blockchain. It may take time and incur network fees, and it requires your own on-chain bitcoin to pay those fees as well as the exit data stored on the device or an emergency package; the KAI-Pay app does not currently carry it out. The providers involved and their roles are set out in the privacy policy.

5. Authorisation, payment proposals and status

Before confirming, check recipient, network, amount, unit and fee limit. QR codes, pasted text and links carry payment data; detection alone is not authorisation. A payment is only initiated once you confirm it in the preview.

This also applies to AI payment proposals. A proposal only pre-fills the send screen and does not replace your authorisation: recipient, amount, unit and fees are shown before every payment and checked against your rules for the source, and nothing is paid until you confirm. You set the allowed recipients and the budget yourself. The purpose of a proposal is stated by the source; we do not check whether it is correct.

The same applies to standing orders: a due date only pre-fills the send screen with a fixed recipient and amount; nothing is paid until you confirm, never automatically. The wallet records paid, pending or skipped due dates only on the respective device; if you create the same standing order on several devices, make sure yourself that you pay only once. A calendar file is only a reminder and does not trigger a payment.

The app identifies prepared, authorised, pending, successful, failed or unresolved transactions. A local “sent” indicator or missing network response proves neither success nor final failure. Check the existing transaction in the activity list before retrying an unresolved payment. Statutory rights concerning faulty software remain intact.

6. Charges, conversion and external fees

We charge nothing for using KAI-Pay, so there is no price schedule. Before your binding confirmation, the app shows the amount, the known third-party network and routing fees and the total separately for every outgoing payment. The fee is shown as a maximum (“Fee (max.)”). A higher total than authorised requires renewed consent. If receiving via a Lightning invoice incurs a fee, the app shows it together with the invoice.

The EUR or USD equivalent shown next to amounts (“≈”) is for display only; no currency exchange takes place. The wallet obtains the conversion rates via the Breez SDK. In the point-of-sale view, an amount entered in EUR is converted to sat at the mempool.space rate; the invoice is denominated in sat. A EUR equivalent does not guarantee future BTC value. Commissions or commercial relationships potentially affecting provider selection are disclosed.

7. Lightning and Spark

Availability depends on connectivity, routes, liquidity and counterparties. We operate no Lightning channels of our own; Lightning payments run via the Spark infrastructure. Payments to Bitcoin addresses, deposits from the Bitcoin blockchain and a unilateral exit to the Bitcoin blockchain may take time and incur additional network fees. KAI-Pay does not offer exchanges into other crypto-assets or tokens. Statutory claims against us or the providers involved remain unaffected.

8. Merchant use of the point of sale

The point of sale is a payment terminal: it requests Lightning payments to the merchant’s Lightning address and shows whether payment was made. It does not record items or goods. Per invoice it stores on the point-of-sale device, among other things, amount, euro amount, rate and receipt number (at most 20 invoices from the past 7 days); the owner’s wallet summarises incoming till payments in “Point of sale & closing”. The point of sale has no technical security device (TSE) and is not a certified till. It is not a substitute for an electronic recording system with a TSE within the meaning of section 146a of the German Fiscal Code (AO) and the German Cash Register Security Ordinance (KassenSichV).

Whether an obligation under section 146a AO and the KassenSichV exists depends on the actual function of the system used, not on its name. We do not promise that the point of sale, “Point of sale & closing” or the payment receipt constitute a legally compliant substitute for a till or fulfil tax, commercial or other recording, receipt and retention obligations.

Merchants remain responsible for their own recording, receipt, retention and tax obligations, in particular for recording their sales in a suitable system and issuing the receipts required. The payment receipt of the point of sale is proof of payment, not a till receipt; the receipt itself says so. “Point of sale & closing” in the wallet is a payment overview, not a till report within the meaning of the KassenSichV. Euro amounts and rates shown there are information from the point of sale; what counts are the sat actually received.

Devices running the point of sale can collect payments but cannot send money; refunds are only possible from the owner’s wallet. The merchant is responsible for instructing staff, checking incoming payments and protecting their own wallet.

9. User responsibilities

Secure recovery information and never share recovery words (seed), private keys or approval codes such as your PIN with us or third parties. Do not use the software unlawfully or circumvent lawful access restrictions. Install the Android test versions only from the pre-releases of our GitHub project, not from other sources. Install required security updates following the provided instructions; the web app indicates when a new version is available. A breach does not automatically remove statutory rights; causation, fault and mandatory law remain relevant. Business users must manage authority and employee permissions.

10. Updates, changes and availability

Supported systems: the web app requires a current browser that provides, among other things, WebAssembly, IndexedDB and Web Crypto over a secure (HTTPS) connection. The Android test versions require Android 7.0 or later; “KAI-Pay” also requires Google Chrome. Some features also depend on browser, operating system and device:

These statements do not shorten statutory update or defect obligations. We inform you about necessary updates and installation; the web app announces new versions with “A new version is available.”, and new Android test versions appear as a pre-release on GitHub. Changes to continuously supplied digital products are subject to applicable law and section 3; relevant adverse changes trigger advance information on a durable medium and statutory termination rights. Silence does not agree to new paid services or material extensions. A specific availability level is promised only where expressly agreed.

11. Termination and restrictions

You can stop using KAI-Pay at any time and delete the wallet from your device in the settings with “Remove wallet from this device”. The app then deletes the access data stored on this device and the wallet database with payment history, contacts and exit data; without your recovery words or passkey, the balance is then no longer accessible. The privacy policy explains what remains, for example at other providers. Statutory termination and withdrawal rights remain intact.

We may restrict our server functions, such as notifications and payment-link pages, as necessary in response to a specific security threat or legal duty. To prevent abuse, our servers also limit the number of requests per IP address. Where permitted, we explain the reason, scope, duration and complaint route. Such a restriction has no effect on your balance; restriction of our service gives us no entitlement to users’ BTC.

At service end we provide agreed export and migration options and explain effects on pending payments and backups. The app already lets you display your recovery words, export your full payment history as a CSV file and save an emergency package. We do not promise technically unavailable recovery.

12. Defects and liability

Statutory remedies for defects apply to the extent they apply to provision free of charge.

We are liable without limitation for intent and gross negligence, including that of our legal representatives and vicarious agents, for damage from injury to life, body or health, under the German Product Liability Act, to the extent of a guarantee expressly given by us, in case of fraudulent concealment of a defect, and in all other cases of mandatory statutory liability, in particular under data protection law.

Otherwise, in cases of slight negligence we are liable only if we breach a material contractual obligation, that is an obligation whose fulfilment makes the proper use of KAI-Pay possible in the first place and on whose observance you may regularly rely. In that case our liability is limited to the damage typical for the contract and foreseeable when the contract was concluded.

To the extent our liability is excluded or limited under this section, this also applies to the personal liability of our legal representatives, employees and vicarious agents. Statutory provisions that further reduce liability for services provided free of charge remain unaffected where applicable. This section does not restrict mandatory consumer rights or the statutory burden of proof.

We are not liable for damage arising from the independent area of responsibility of an external purchase provider (section 15) unless we have ourselves committed a breach of duty giving rise to liability.

General risk warnings do not replace due care or excuse our own breaches. Technical irreversibility does not eliminate legal reimbursement or damages claims.

13. Copyright, rights of use and licences

Rights in the KAI-Pay software, that is in the wallet, Android apps, point of sale and payment-link pages, and in the texts and design of this website belong to Formsys GmbH or its licensors, to the extent such rights exist. The open-source components included are excepted.

For the duration of use, we grant you the simple, non-transferable right, free of charge, to use the software in the form provided on your devices as intended, for merchants also in their own business. Acts permitted by law, for example under sections 69d and 69e of the German Copyright Act (UrhG), remain unaffected. You may use our marks beyond the intended use of the app only with our consent.

Open-source components included are subject to their own licences; these terms do not restrict them. The wallet and the point of sale ship the components with version, licence and full licence text including copyright notices with every version: wallet licence notices, point-of-sale licence notices. In the wallet and in the app “KAI-Pay Beta” you also find them under “Settings” → “Legal” → “Open-source licences”. The list is regenerated whenever the libraries change; its date is stated at the top. The components are under permissive licences such as MIT, Apache-2.0, BSD, CC0, Unicode-3.0 and Zlib. Our server creates the QR codes of the payment-link pages with qrcode-generator (MIT, github.com/kazuhikoarase/qrcode-generator).

Your recovery words, keys and balance remain yours, as do your payment data, contacts, notes and exports. These terms give us no rights in them. We process what you enter only as far as the respective function requires (privacy policy).

14. Law, language and disputes

German law applies. Consumers retain mandatory protections of their habitual residence under applicable conflict-of-laws rules. Statutory consumer jurisdiction applies; no exclusive jurisdiction is imposed to consumers’ disadvantage. The language version selected at contract formation is provided; discrepancies cannot reduce mandatory rights. Statutory rules apply if a term is invalid; there is no automatic replacement with the commercially strongest permissible clause.

15. External purchase providers

Role of KAI-Pay

Within KAI-Pay, Formsys GmbH provides under “Buy bitcoin” a link to an external provider for acquiring bitcoin, currently Strike (provider: Zap (Strike) Europe Limited, Malta). Through this link function we do not accept purchase orders, do not transmit purchase orders to the provider and do not execute purchases. Nor does the link feature itself forward a private key, invoice or wallet address to Strike. A third-party provider you visit receives its own connection data. In doing so we neither accept nor hold in custody purchase funds or the bitcoin acquired from the provider on your behalf.

The contract for the external bitcoin purchase is concluded exclusively between you and the provider named there. The contractual relationship for the use of KAI-Pay remains separate from it.

Choice of provider and information

Providing the link contains no investment advice based on personal circumstances and no promise that the provider is suitable for every user or the cheapest provider. We receive no remuneration for the link.

Information on fees, availability and supported payout methods may change. For the specific purchase, the information provided by the external provider before the transaction is concluded is decisive. Our responsibility for our own incorrect or misleading information remains unaffected.

Payout and support

Identity checks, purchase processing, refunds and payouts at the external provider fall within its area of responsibility. We cannot control its decisions or processing times. We remain the point of contact for technical problems within KAI-Pay.

Before a payout, receiving details, network, amount and, where applicable, the validity of a Lightning invoice must be checked. Successfully executed bitcoin transactions generally cannot be reversed. Statutory claims in the event of errors on our part remain unaffected.

Availability of the link

We may remove the link or switch it off temporarily for security reasons, because of changed regulatory requirements or if the offer is discontinued. Claims of users that have already arisen remain unaffected.