Can anyone break MD5 scheme?

[cyber_armstrong <cyber_armstrong () yahoo co uk>]

I paid a high monthly fee for my PPPOE connection. The damned ISP 
offered only the client for M$ Windows. According to the packet dump, 
they use CHAP for authorization and the CHAP challenge  said it used 
MD5. But when rp-pppoe MD5s the string of Identifier+Secret+Challenge 
Value, the concentrator said the response is wrong.

Apparently the ISP-offered client is not going with the RFC 1994 
standard for CHAP and obviously I cannot get their source code by social 
engineering.

/Is there a way to break the MD5? Or anyway around ? /I  need to know my 
ISP's digest scheme to get my Linux box online. I lived in a 
higly-sensored country and who knows what the offered client will do 
behind my back? Thanks in advance for my safety (not privay).

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