The Jargon File (version 4.4.7, 29 Dec 2003):

rubber-hose cryptanalysis
 n.

    [sci.crypt newsgroup] The technique of breaking a code or cipher by finding
    someone who has the key and applying a rubber hose vigorously and
    repeatedly to the soles of that luckless person's feet until the key is
    discovered. Shorthand for any method of coercion: the originator of the
    term drily noted that it ?can take a surprisingly short time and is quite
    computationally inexpensive? relative to other cryptanalysis methods.
    Compare social engineering, brute force.