Add string to create specific MD5?

I have a file that include a long string , I can calc the md5 of this file .

Is there any way to know which string I need to add for this file so the md5 of this file will be specific md5 that I want?

For example , if I have string 111222333444 the md5 of this string is 092d75d9d14011469f281795901bdd1b if I want the md5 of my string string will be f45b563d2ecf032da2ce3416ba8f518e I need add to this string AAAA , so the string will be 111222333444AAAA

• Welcome to Cryptography. You are looking for an MD5 collision. This is rather off-topic here. – kelalaka Feb 2 '19 at 22:10

Finding a specific md5 output value is known as a preimage attack. While md5 is very broken for collision resistance, the preimage resistance is still impractical. There are some papers with run times slightly less than the theoretical maximum, but these are still extremely expensive (e.g. cost $$>2^{100}$$). Your base string ("fixed prefix") may make some of the attacks not work, which will make it even more expensive to find an additional string to add.