Electroporation is an effective method to deliver drugs into tumor cells to kill them, by applying a pulsed electric field to the cellular membrane. Existing electrodes consist of clamping claws or arrays of needles and can be effectively applied only to small areas. New electrodes that can treat large areas are sought; flexibility is needed to adapt to irregular tumor shape and, to be folded to enter from small surgical opening. In this work we present the design and test of a 16 cm ² flexible electrode for electroporation with biosensing capabilities, built with standard flexible circuit technologies enclosed in a biocompatible package. The electrode contains electronics to provide cryptography-based identification to the electroporation machine to avoid setup errors and protection against use of counterfeited electrodes. In-vitro tests of the electrode show that electroporation occurs up to a depth of 8 mm with 100% electroporation efficiency over the 30% of electrode area. Temperature rise on the electrode during treatment does not exceed 6 degrees celsius, a value that not causes damage to the cells.