An initialization vector is employed to decrypt a block of a stream that has been encrypted with Cypher Block Chaining encryption, without requiring decryption of previous blocks within the stream. Further activity may include transforming the split-keys to provide N encrypted split-keys, and storing each of the encrypted split-keys with an associated local user identity and an identity of corresponding ones of the authentication mechanisms. The hybrid hinge 7, 8 comprise respective rigid hinges 2, 4 arranged to rotate the segments S1, S2, respectively S2, S1\u2032 about respective shafts 2, 4. A controller is in communication with the exterior open switch, the interior open switch, and the electric door latch mechanism. A pair of spaced stand assemblies, each including a latching mechanism, support the snowplow assembly when the mount frame is separated from the snowplow assembly.