According to the filing, CertCo filed suit Monday in U.S. District Court in Delaware, charging that PayPal had infringed its patent no. 6,029,150, which covers a type of online payment system. Charging that PayPal had engaged in "willful" infringement of that patent, CertCo, which has held the patent since February 2000, asked the court for a permanent injunction against PayPal and an unspecified amount of damages, according to the regulatory filing.