Secure online transaction system and method therefor

A method for completing a transaction session, the method comprising:

• starting the transaction session;
• sending at least a first data set from a merchant subsystem to a client computing device, said first data set unrelated to said transaction;
• sending at least a second data set from a secure subsystem to the client computing device;
• receiving at least a third data set related to said transaction;
• and
• completing the transaction session using at least said third data set, such that the merchant subsystem is excluded from accessing said second and third data sets,

One or more non-transitory storage devices storing computer-executable instructions for completing a transaction session, wherein the instructions, when executed, cause a processor to perform actions comprising:

• receiving a first data set from a merchant subsystem, said first data set unrelated to said transaction;
• receiving at least one or more UI components and one or more client-side application programs from a secure subsystem;
• displaying said one or more UI components;
• collecting a transaction-related data set from a client;
• executing said one or more client-side application programs to encrypt said collected transaction-related data set;
• and
• sending the encrypted transaction-related data set to a transaction processing subsystem for completing the transaction session.