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I searched in google about the generation of windows 95 oem key Keys have the pattern **XXXXX-OEM-XXXXXXX-XXXXX**

The first part is 3 first digits are the day of the year and the 2 last are the year (95-03)

July 3rd was the 184th day of 1999 so the first part is 18499

The second part first digit is 0 and sum of the 6 more must be divisible by 7 I chose 0123456

Part 3 is just random numbers - unchecked

The key I used was 18499-OEM-0123456-11111 After going to http://ch1.sbug.se/?license=18499-OEM-0123456-11111 I got the flag

> SBCTF{CR4CK1NG_95_W4S_N0T_TH4T_H4RD}

**bonus** Win 95 had a lot of good keys and so there are to get the flag The exact number is 142880 * 10^5 = 14288000000 (from part 3 and 4)