 Multimode fibers offer great potential for increasing data rates in optical communications, but they come with the challenge of compensating for modal cross-doc and mode-dependent losses, leading to strong distortions. Holographic measurements of the transmission matrix enable not only correcting these distortions, but also harnessing them for creating a confidential data connection between Alice and Bob. This physical layer security-based approach was demonstrated experimentally for the first time on a multi-mode fiber link with the eavesdropping eave physically coupled to it. By launching the appropriate structured light field at Alice's side, the message could be delivered to Bob while simultaneously destroying the deciphering for Eve. In a real communication scenario, wiretap codes were implemented and the amount of securely exchanged data was increased by a factor of 538 compared to an uncoded data transmission. These complex light transportation phenomena that had previously been seen as limiting and restrictive were instead used to open up new perspectives on information security in spatial multiplexing communication systems. This article was authored by Stefan Roth, Carl Ludwig Besser, David Krause, and others. We are article.tv, links in the description below.