Hello Monks! After searching, I found many nodes complaining that md5_hex producing different output from identical input. I have the opposite problem. I have different input producing identical output! I'm trying to index my websites visitor logs so I call md5_hex on a string that consists of (state,city,resolution,lang,user_agent, browser plugins) concatenated together. Some of these values are passed via javascript/hidden form elements. My thinking was that this would be diverse enough to produce "fingerprints". However, I've been getting some duplicate fingerprints with different data for example: 
$string1="CA" . "Los Angeles" . "1440x900" . "en-us" . "Mozilla/4.0 (c
+ompatible; MSIE 6.0; Windows NT 5.1; SV1)" . "";

$string2="CA" . "Los Angeles" . "1280x1024" . "en-us" . "Mozilla/4.0 (
+compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; Medi
+a Center PC 5.0; .NET CLR 3.0.04506)" . "";

[download]
Both produced '40d704470259297f93bee626c12b71fb' as output. This cgi script is running on a load balanced server and inserting records into a central database. Not using mod_perl. Does MD5 not use the whole string? Any light that you could shed would be appreciated. Oaty

In reply to md5_hex diff input produces same output? by Oaty

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