In the secure electronic transaction set, the cardholder needs to send two pieces of information to the supplier when shopping, that is, the purchase order information OI and the encrypted payment card information PI. OI is sent to the supplier, and the encrypted PI is transferred to the payment gateway bank through the supplier. The OI and PI of the same transaction are interrelated, and both message abstracts have double signatures, which can prove the authenticity of OI and PI to suppliers and banks respectively.