A pre-certified payment application driver code configured to satisfy requirements of a particular level of a credit card data security certification compliance may be integrated with first and second POS applications to generate first and second integrated applications, respectively, as a fully integrated, tested and production-ready solution. Each integrated application meets all levels of data security compliance requirements and enables data security-compliant transactions with end-to-end encryptions by enabling, in response to a POS application initiating a payment transaction, a payment terminal to share an encryption key with a payment server. Each integrated application can receive payment data encrypted with the encryption key, transmit the encrypted payment data to the payment server for processing the payment transaction using the encrypted payment data, and receive a processing result of the payment transaction from the payment server and communicate the processing result to the POS application.