Is a Bitcoin timestamp valid legal evidence?

It can be used as evidence. A Bitcoin timestamp proves mathematically that a fingerprint of a file existed before a specific block was mined, and anyone can check it independently. In the EU, eIDAS says an electronic time stamp cannot be denied legal effect or admissibility just because it is electronic, though only qualified time stamps get an automatic presumption of accuracy. How much weight a court gives it depends on the case, so it works best as strong supporting evidence alongside your other records.

How it works

1. Hash the file. Only the fingerprint is timestamped, never the content.
2. The fingerprint is folded into a Merkle tree whose root is written into Bitcoin through OpenTimestamps.
3. Anyone can recompute the proof with free tools, without trusting the issuer.
4. Keep the original file safe: the proof only works with the exact same bytes.