You have the option of letting LTI do all of the authentication (i.e. users can only get to WeBWorK through the LTI link in D2L), or you can have LDAP set up as well, so users can also log directly into WeBWorK. I have our server set up this way, since not all of our courses are linked to a D2L course.
WeBWorK Main Forum
Integrating WW with Desire2Learn?
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