eCertificate

Product type

Digital rental deposit certificate with blockchain notarisation

Issuer

goCaution AG, Bern

Blockchain layer

Arbitrum One (Ethereum Layer 2, Optimistic Rollup)

Notarised object

SHA-256 hash of the PDF certificate (no personal data on chain)

Smart contract address

{TODO: insert on-chain address once publicly documented}

Mainnet deployment

{TODO: deployment date and transaction hash}

Explorer

arbiscan.io

Format

PDF with embedded QR code and visible hash

Verification

Via QR code scan or PDF upload at gocaution.ch/verify

Launch year

{TODO: first deployment / first productive issuance}

1. goCaution generates the deposit certificate as a PDF document.
2. A SHA-256 hash (64-character hexadecimal fingerprint) of the PDF is computed.
3. The hash is persistently registered in a smart contract on the Arbitrum blockchain. Only the hash, a timestamp and status metadata are stored on-chain — no plaintext tenant, landlord or property data.
4. The finalised PDF is delivered to the landlord and archived in the landlord portal.
5. For verification the verifier scans the QR code or uploads the PDF to gocaution.ch/en/verify. The hash is computed in the browser; the PDF never leaves the verifier's device.
6. The hash is matched against the blockchain. Match = the certificate is authentic and unchanged.

Hash computation

Locally in the verifier's browser (SHA-256 via Web Crypto API)

Data transmitted

Only the 256-bit hash is sent, not the PDF

Lookup

goCaution server forwards the hash to the CRM and the smart contract

Response

Certificate status (valid, revoked, unknown) plus blockchain transaction hash

Response time

Typically < 3 seconds

Data protection

Personal data are not disclosed to the verifier; only technical validity

• Not an NFT: The eCertificate is not a non-fungible token in the ERC-721/ERC-1155 sense. It is not a tradeable asset; it cannot be transferred, sold or exchanged.
• Not a cryptocurrency: No crypto wallet is required to receive or verify an eCertificate. The blockchain serves exclusively as a notarisation registry, not as a payment medium.
• No public plaintext: Only the document hash is stored on chain. Names, addresses, deposit amounts and contract details are not retrievable on-chain.
• No smart contract for payments: Payouts in case of a claim are processed exclusively via the traditional contractual chain between goCaution, the underwriting insurer and the landlord. The blockchain does not settle any cash flows.
• Not a qualified electronic signature (PAdES/ZertES): The eCertificate is not a qualified electronic document under the Swiss ZertES framework. Its integrity relies on hash comparison against the blockchain, not on an embedded X.509 signature.

• Cost structure: Arbitrum transactions typically cost less than one Swiss cent; Ethereum mainnet transactions fluctuate between cents and several francs.
• Public verifiability: Unlike a private chain, anyone can independently verify the notarisation via arbiscan.io — a key trust argument.
• Ethereum security anchor: Arbitrum is an Optimistic Rollup and inherits Ethereum's finality guarantees. Manipulation would require an attack on Ethereum itself.
• Migration capability: Arbitrum addresses are Ethereum addresses; migration to mainnet or another EVM chain is technically feasible.

The public blockchain stores only technical data: document hash, timestamp, status. Personal data (name, address, property, deposit amount, credit data) reside on goCaution servers in Switzerland (ISO 27001-certified) and are subject to the Swiss Federal Act on Data Protection (revFADP) and EU GDPR.

A re-identification of a specific person from the blockchain hash is not possible, as the hash is derived from a non-deterministic document content.

Each issued eCertificate replaces a paper document and, under the partnership with CARBONconnect (“Treellionnaire” campaign), triggers the planting of a tree. Arbitrum itself — like Ethereum since the Merge in September 2022 — runs on Proof-of-Stake, consuming roughly 99 % less energy than the former Proof-of-Work Ethereum.

The eCertificate is accepted in the Swiss real estate industry as an equivalent replacement for a paper certificate. Delivery is by email to the landlord (or the responsible property manager) and additionally through the goCaution landlord portal. On request the PDF can also be printed and sent by post.

• eCertificate product page (EN): gocaution.ch/en/ecertificate
• Verification tool: gocaution.ch/en/verify
• Arbitrum documentation: docs.arbitrum.io
• Arbiscan (blockchain explorer): arbiscan.io
• goCaution AG company facts: gocaution.ch/en/facts/gocaution