<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><DIV>The same as what wikipedia describes it:</DIV>
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<P><B>Single sign-on</B> (<B>SSO</B>) is a method of <A title="Access control" href="http://en.wikipedia.org/wiki/Access_control">access control</A> that enables a user to <A class=mw-redirect title="Log in" href="http://en.wikipedia.org/wiki/Log_in">log in</A> once and gain access to the resources of multiple software systems without being prompted to log in again. <B>Single sign-off</B> is the reverse process whereby a single action of signing out terminates access to multiple software systems.</P>
<P>As different applications and resources support different authentication mechanisms, single sign-on has to internally translate to and store different credentials compared to what is used for initial authentication.</P>
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