Proof of Existence can be used to register document's copywrite or patent, by saving the target document's hash value into Asch sidechain so that the existence of this document can be proven. Practically some other meta-data, such as timestamp or participants' digital signature, can also be appended to prove since when had they possessed these documents. All of the privacy information cannot be forged, distorted, or exposed, and if necessary, the information can be verified easily without any help from thirt-party institutions.