Methods, computing systems and computer program products implement embodiments of the present invention that include defining multiple primitives, each of the primitives including ranking and unranking methods. Two or more of the multiple primitives are selected, and an operation is performed on the selected primitives, thereby defining a complex format. Upon an encryption processor receiving a data record including a plaintext, the complex format is applied to the plaintext, thereby generating a non-reversible token. In some embodiments, the generated token is transmitted a remote computer.