Electronic Signatures Act Article 6

Where a digital signature employed in an electronic record satisfies the following requirements, it shall be presumed as the signature or seal affixed in person:(1) it shall be supported by a certificate issued by a certification authority which have been approved by the competent authority in accordance with Article 12 or Article 15; and(2) the certificate has not exceeded its validity period and its limitation of use.
中文原文 電子簽章法第6條
以數位簽章簽署電子文件,符合下列各款規定者,推定為本人親自簽名或蓋章:
一、使用經主管機關依第十二條或第十五條許可之憑證機構簽發之憑證。
二、憑證未逾有效期間及其使用範圍。

English translation for reference only; the Chinese text prevails. Not legal advice.