A dongle is a small hardware device that connects to a computer to authenticate some piece of software. This was its primary meaning in the computer industry in the 1980s and 1990s. When the dongle is not present, the software runs in a restricted mode or refuses to run. Dongles are used by some proprietary vendors as a form of copy prevention or digital rights management because it is much harder to copy the dongle than to copy the software it authenticates.
Software protection dongles are typically used with very expensive packages (starting with about USD 500 and up) and vertical market software, such as CAD/CAM software, Digital Audio Workstation applications and some translation memory packages. Efforts to introduce dongle copy prevention in the mainstream software market were generally met with stiff resistance from users. Despite being hardware, dongles are not a complete solution to the trusted client problem.
Vendors of software protection dongles (and dongle-controlled software) often use terms such as hardware key, hardware token, or security device in their written literature. In day-to-day use however, the jargon word "dongle" is much more commonly used.
Dongle can also refer to something that plugs into a computer, especially something with wires that "hang" (dangle) from a laptop computer. For example:
Well-known software protection dongle manufactures include SafeNet, Aladdin and WIBU-SYSTEMS.
Dongle as the name of a device was used well before 1980 within the telecoms industry to refer to BNC cable joiners of either sex (such as the RG58 cable used on 10 meg Ethernet).
WORDCRAFT was the first program to use a software protection dongle, in 1980. Its dongle was a simple passive device that supplied data to the pins of a cassette port in a pre-determined manner. That first dongle was invented and named by Graham Heggie in the UK.
The two cubic inch (33 cm³) resin-potted first generation devices were called "dongles" by the inventor as there was no other suitable term to hand on the day. The device increased WORDCRAFT sales significantly. The distributor, Dataview Ltd., then based in Colchester, UK, then went on to produce a derivative dongle which became their core business.
Dongles rapidly evolved into active devices that contained a serial transceiver (UART) and even a microprocessor to handle transactions with the host. Later versions adopted the USB interface in preference to the serial or parallel interface.
There is the potential for weaknesses in the implementation of the protocol between the dongle and the copy-controlled software. It requires considerable cunning to implement this in a fashion that is not easy to crack. For example, naïve implementations might simply define a function to check for the dongle, returning "true" or "false" accordingly, reducing the prevention scheme to a single bit value at one point in the program.
Modern dongles include built-in strong encryption and use fabrication techniques designed to thwart reverse engineering. Typical dongles also now contain non-volatile memory — key parts of the software may actually be stored on the dongle. Thus dongles evolved and have become secure cryptoprocessors that execute inaccessible program instructions that may be input to the cryptoprocessor only in encrypted form. The original secure cryptoprocessor was designed for copy protection of personal computer software (see US Patent 4,168,396, Sept 18, 1979) to provide more security than dongles could then provide. See also bus encryption.
However, security researchers warn that dongles still do not solve the trusted client problem: that if you give a user the cryptographic ciphertext, the algorithm and the key, your cipher is likely to be breakable, even with the algorithm and key encoded in hardware. (Grand, 2000)
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