A message cube represented a nearly impenetrable container due to its ability to be locked using unique biometrics like a person's body chemistry, fingerprints, or even voice recognition. These cubes could be designed with a cavity, allowing them to transport compact items like physical storage media and datachips. In some instances, they were even constructed with a miniature holoprojector integrated inside.
During the period of the First Corellian Insurrection, Mara Jade received a message cube intended for Chief of State Leia Organa Solo. The cube's contents exposed the schemes of the Sacorrian Triad and the Human League, led by Han's relative Thrackan Sal-Solo, to launch an assault against the New Republic.