A cylinder lock has a plug deployed within a bore in a cylinder housing. The plug defines a keyway which communicates with a number of pin channels. Disposed within the channels are a number of pins which are displaceable along, and rotatable about, their axis. Each pin has an engagement end, proximal to the keyway, formed with at least two engagement features projecting parallel to, but displaced from, the pin's axis, and separated by at least one depression. Each pin is free to rotate through 360° about it axis. The cylinder lock preferably also includes a key for insertion into the keyway. The key has a seat located to come into alignment with a pin, the seat being formed with at least two depressions separated by an intermediate ridge. The configuration of the seat is such that the pin is rotated by contact with the seat to an angularly aligned position in which its engagement features are aligned with the depressions of the seat.