Negative Adjective - くない　vs くはない

Hello. So I'm going through some listening series for Japanese, and one of the phrases in one lesson was "not wanted/not desired". With wanted/desired being ほしい, I was expecting ほしくない, but instead they were saying ほしくはない (or くわない, all my searches for an answer so far have suggested it was the particle は). The sample sentence was きっぷがほしくないです。 Can anyone explain whether one of these forms is wrong, or if both are correct, what the implications of each would be? Thanks!

Both are possible. 〜くない is the plain negative.

は adds an element of contrast/partial negation. You often see it with "but.."
ほしくはないけど... (I don't want it, but...)
多くはない (There's not many)