nanalLabs BlogA recurring defense in patent disputes is the prior-use right. Article 103 of Korea's Patent Act (non-exclusive license by prior use) grants a party who was already practicing an invention — or preparing to — before someone else filed for it, the right to keep practicing within that scope. The exact text is available (in Korean) at casenote.kr. Most patent systems, including Europe's and the United States', have a comparable doctrine.
The issue is always proof
The hard part is proving "we were already building this." A Korean patent office guide for small businesses (PDF, Korean) lists, citing a 2006 report by the Japan Patent Office, the kinds of evidence that support a prior-use claim: research notebooks, technical reports, drawings and product specifications, plus business records such as plans, estimates, delivery slips, and daily work logs. It also names ways to strengthen that evidence — notarization, and private timestamps and electronic signatures — and stresses that what matters most is to "create and preserve evidentiary records in the course of daily work, in a way that can prove when they were written."
In other words: the claim itself is worth little. What decides the outcome is dated records.
What the original-proof service certifies — and what it doesn't
Trade-secret disputes have the same structure. Korea's original-proof service registers a digital fingerprint (hash) of a file with a certification body; in a dispute it certifies existence, holder, and time of possession. In January 2025, three private organizations were additionally designated as certification bodies.
But an original-proof certificate only certifies "this file existed at this time." To be protected as a trade secret you must separately prove confidentiality management, economic value, and non-disclosure — and a prior-use defense is not granted on a certificate alone. It needs the substance: plans and experimental data, recorded as the work happened.
Where practice breaks down
The original-proof service registers files one at a time. That works for proving a single document, but it cannot realistically keep up with records that accumulate daily — and prior-use evidence is precisely that: an unbroken timeline of day-by-day records, not a single snapshot.
So everything converges on one question: not "can we certify this one document," but "do our daily records survive, in order, with verifiable timestamps, without gaps?"