Offline authentication method for paper invoices

The invention discloses a paper invoice offline authentication method, which is specifically executed according to the following steps of: firstly, automatically generating an ECDSA public and private key pair on a security chip on an invoicing terminal, and sending the ECDSA public and private key pair to a tax bureau side; after the tax bureau side receives the request of the terminal, the root certificate of the PKI system generates a corresponding public key certificate and issues the equipment certificate to the invoicing terminal; when invoicing software on the invoicing terminal issues an invoice, the ECDSA private key signs main elements of the invoice to generate a two-dimensional code; the verification APP on the intelligent terminal performs verification, when the intelligent terminal is offline, the verification APP scans the two-dimensional code for verification, and after the certificate is verified, the signature value in the two-dimensional code is verified according to the main elements of th