"Rubberhose Cryptography formed the kernel of TrueCrypt — a program where folders on a drive can be protected by a password, but where the folders are themselves able to contain hidden folders which are only revealed by another password"

https://medium.com/@niraj.lal/rubberhose-cryptography-and-the-idea-behind-wikileaks-julian-assange-as-a-physics-student-4fd0578cbaa3