An installation mechanism that securely installs encrypted software modules on a computer is described. The mechanism allows restricted software, such as domestic strength cryptography software, to be shipped directly to a user. The mechanism decrypts the software modules and installs the software modules on the computer only when at least one of a set of trigger files is present on the computer, thereby requiring that the computer be authorized for the restricted software. A setup program invokes each of a plurality of installation modules in order to install the software modules. Each installation module securely encapsulates an encrypted version of the software module and is programmed to decrypt the corresponding software module only when a genuine trigger file is detected.