A method of improving privacy by hiding, in an ordered sequence of messages M[x(1), D(1)], M[x(2), D(2)], etc, communicated between a first and at least one second party sharing a key k, metadata x(i) descriptive of message processing, wherein D(i) denotes payload data. The method comprises the first and the second party agreeing on a pseudo random mapping depending on a shared key k, Fk, mapping at least x(i) to y(i), and the first party modifying the messages by replacing x(i) by y(i) in each message M(x(i), D(i)). The first party then transmits the modified messages maintaining their original order, and on reception of a message M(y(m), D), the second party uses a mapping Gk to retrieve position m of received value and the original value x(m).