Challenger is described as 'Software for the encoding of files, folders and drives. For the installation and for the execution simple user rights suffice. Thereby the program is mobil usable on an USB flash drive too' and is a Disk Encryption tool in the security & privacy category. There are more than 50 alternatives to Challenger for a variety of platforms, including Windows, Mac, Linux, Android and iPhone apps. The best Challenger alternative is TrueCrypt, which is free. Other great apps like Challenger are GnuPG, Kleopatra, Axcrypt and Windows BitLocker.