I've been working with this module as well and encountered the same SOAP error. The problem is that the function that creates the context stream, SoapClientHMAC(), was put in the wrong place. As a result, the context stream is never actually created, so a NULL is passed to the stream_context_set_option() function, which causes an error. If you move the entire "function SoapClientHMAC()" block into the SoapClientHMAC class, it fixes the error.
Also, there is no need to change your password to something shorter. Instead, change the substr() lengths from 16 to 32, which is the current maximum.
I submitted an update to this module that includes these fixes: https://apps.oscommerce.com/OHF0I&first-data-global-gateway-e4-aim
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