IIRC at one point the AIM server started doing a challenge: "send me N bytes at offset X of the aim.exe binary". I recall the open-source AIM clients themselve

IIRC at one point the AIM server started doing a challenge: "send me N bytes at offset X of the aim.exe binary". I recall the open-source AIM clients themselves set up a service that would return substrings of the binary so that their open-source clients could continue to login without needing to ship a copy of the binary.