Data anchoring and timestamping

Data anchoring services (앵커링) take a fingerprint, a hash, of your files, logs or records and anchor it to a public blockchain or another tamper-evident ledger, so you can later prove the data existed at a point in time and has not changed since. Compliance and audit-log teams, legal and IP teams proving authorship, supply-chain and media-provenance projects use them. They differ in what they anchor to, what proof you keep, whether your content ever leaves your systems, and how they bill: by offer, per ledger message, per certificate or by plan.

We compare them on the same six indicators, read from each vendor's pricing, security, legal and documentation pages:

• Pricing clarity: whether prices are published and can be bought online, and whether the pages leave prices out or contradict themselves.
• Free tier: a free plan with API access to a production chain, a free web tool, or only a test network.
• Price for 100,000 hashes: the lowest listed monthly cost to anchor 100,000 SHA-256 hashes a month through an API, each with its own proof, with the arithmetic shown; 0 when the pages cannot price it.
• Proof independence and privacy: how many public chains, a proof you keep, verification without the vendor, hash-only submission and deletion.
• Compliance and legal standing: the vendor's own SOC 2 Type II, ISO 27001, eIDAS-qualified or RFC 3161 timestamps, and court decisions the vendor cites.
• Developer and team features: API, SDKs, webhooks, batch submission, SSO, team roles and an audit log.

How often a vendor anchors to a chain is a product spec we state where the vendor does, but do not score. Each review says which pages it was written from and when. Where we have run a product hands-on, the evidence is on its page.