Dongle

A dongle is a small piece of hardware that connects to and protrudes from a laptop or desktop computer. Electrically, dongles mostly appear as two-interface security tokens with transient data flow that does not interfere with other dongle functions and a pull communication that reads security data from the dongle.

These are used by some proprietary vendors as a form of copy protection or digital rights management, because it is generally harder to replicate a dongle than to copy the software it authenticates. Without the dongle, the software may run only in a restricted mode, or not at all.

Efforts to introduce dongle copy-protection in the mainstream software market have met stiff resistance from users. Such copy-protection is more typically used with very expensive packages and vertical market software, such as CAD/CAM software, MICROS Systems hospitality and special retail software, Digital Audio Workstation applications, and some translation memory packages. In cases such as prepress and printing software, the dongle is encoded with a specific, per-user license key, which enables particular features in the target application.

This is a form of tightly controlled licensing, which allows the vendor to engage in vendor lock-in and charge more than it would otherwise for the product. Some software developers use traditional USB flash drives as software license dongles that contain hardware serial numbers in conjunction with the stored device ID strings, which are generally not easily changed by an end-user.

A developer can also use the dongle to store user settings or even a complete "portable" version of the application. Not all flash drives are suitable for this use, as not all manufacturers install unique serial numbers into their devices.

Although such medium security may deter a casual hacker, the lack of a processor core in the dongle to authenticate data, do encryption/decryption, and execute inaccessible binary code makes such a passive dongle inappropriate for all but the lowest-priced software.

A simpler and even less secure option is to use unpartitioned or unallocated storage in the dongle to store license data. Common USB flash drives are relatively inexpensive compared to dedicated security dongle devices, but reading and storing data in a flash drive are easy to intercept, alter, and bypass.