<algorithm> (Or "message digest function") A {one-way function} which takes a variable-length message and produces a fixed-length hash. Given the hash it is computationally infeasible to find a message with that hash; in fact one can't determine any usable information about a message with that hash, not even a single bit. For some one-way hash functions it's also computationally impossible to determine two messages which produce the same hash. A one-way hash function can be private or public, just like an encryption function. MD5, SHA and Snefru are examples of public one-way hash functions. A public one-way hash function can be used to speed up a public-key digital signature system. Rather than sign a long message, which can take a long time, compute the one-way hash of the message, and sign the hash. {sci.crypt FAQ (ftp://src.doc.ic.ac.uk/usenet/usenet-by-group/sci.crypt/)}. (2001-05-10)

<communications> A channel (on a BRI or PRI line) used to carry control information, to set up connections on the associated bearer channels. The name wasn't too bad back when users were sending voice (not data) over the {bearer channels}, but in 1997 it's quite a misnomer. (1997-03-10)

Channel was the name of a lightvessel station located in the English Channel between 1979 and August 2021, when it was replaced with a light buoy. It was also one of the 22 coastal weather stations whose conditions were reported in the BBC Shipping Forecast.

Sodium channel blockers are drugs which impair the conduction of sodium ions (Na+) through sodium channels.

Abyssal channels (also, deep-sea channels, underwater channels) are channels in Earth's sea floor. They are formed by fast-flowing floods of turbid water caused by avalanches near the channel's head, with the sediment carried by the water causing a build-up of the surrounding abyssal plains.

The Brač Channel () is a channel in the Adriatic Sea between the Dalmatian mainland and the island of Brač.

The SOFAR channel (short for sound fixing and ranging channel), or deep sound channel (DSC), is a horizontal layer of water in the ocean at which depth the speed of sound is at its minimum. The SOFAR channel acts as a waveguide for sound, and low frequency sound waves within the channel may travel thousands of miles before dissipating.

BK channels (big potassium), are large conductance calcium-activated potassium channels, also known as Maxi-K, slo1, or Kca1.1.

The Velebit Channel (, or ; or ) is a channel in Croatia located between the lands at the foot of the Velebit mountain range and the islands of Pag, Rab, Goli Otok, Prvić and Krk. It is about long, with an average width of and up to deep.

In computer security, a covert channel is a type of attack that creates a capability to transfer information objects between processes that are not supposed to be allowed to communicate by the computer security policy. The term, originated in 1973 by Butler Lampson, is defined as channels "not intended for information transfer at all, such as the service program's effect on system load," to distinguish it from legitimate channels that are subjected to access controls by COMPUSEC.