Exetools Find the Algorithm
 Register Forum Rules FAQ Calendar Mark Forums Read

 Notices HTTP connection will be closed soon. Please visit eXeTools with HTTPS in the future. https://forum.exetools.com This is the ONLY ONE domain that we use. Follow @exetools on Twitter and send me a message, I will choose whether to send the invitation code. Any password problems please mailto: 883600(at)qq(dot)com

#1
05-12-2020, 05:31
 mcr4ck Friend Join Date: Nov 2019 Posts: 19 Rept. Given: 0 Rept. Rcvd 1 Time in 1 Post Thanks Given: 17 Thanks Rcvd at 1 Time in 1 Post
Find the Algorithm

I want to find the algorithm for calculating numbers
But I couldn't
plese help

input ===> out put

15 7d 78 89 ===> b2 80 e8 40
01 02 03 04 ===> 91 7c e7 7d
00 00 00 00 ===> 97 7E 4F 1E
01 01 01 01 ===> 80 04 6A BD
FF FF FF FF ===> 6D EF 8B 38

I wanted to find algorithm
#2
05-21-2020, 18:41
 LaDidi VIP Join Date: Aug 2004 Posts: 176 Rept. Given: 2 Rept. Rcvd 11 Times in 10 Posts Thanks Given: 16 Thanks Rcvd at 21 Times in 15 Posts
@mcr4ck :
You can't with 4 examples and maybe with more...
Are-you sure only DWORD is an input ?
If so, you can try :
• 00000000
• 00000001
• 00000010
• ...
to find a pattern
#3
05-26-2020, 11:37
 psgama Friend Join Date: Jul 2014 Posts: 80 Rept. Given: 0 Rept. Rcvd 3 Times in 3 Posts Thanks Given: 8 Thanks Rcvd at 64 Times in 38 Posts
Yes, need to find pattern and more example.
Put in spreadsheet and calculate delta input vs delta output. Look for pattern, like consistent remainders when you divide by the delta. Some common algorithm I’ve seen divide by prime number and use MOD function.

Try patterns with equal value between inputs to see how output tracks.

Good luck!
#4
05-26-2020, 18:19
 chants Family Join Date: Jul 2016 Posts: 515 Rept. Given: 5 Rept. Rcvd 34 Times in 20 Posts Thanks Given: 434 Thanks Rcvd at 780 Times in 361 Posts
It's possible the smallest algorithm is close to a 16gigabyte lookup table where the nth element is the corresponding output. This would be the case if the output was a random permutation of the input. In fact this could be done easily in modern computers via keeping the table on the disk.

In practical terms, all you can do is try to find patterns or check known algorithms. Even if you had all 4 billion combinations though, there is no known way to compress it from a switch statement lookup into an elegant or eve maximally compressed algorithm. This is basically a trial and error task and 4 values won't be enough. In fact you would want a good percentage of the state space before trying statistical analysis. The NIST statistical testing framework might give an idea of weaknesses though where it's not sufficiently random. Starting from a black box it's a good starting point sometimes
 The Following User Says Thank You to chants For This Useful Post: Abaddon (05-27-2020)

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is Off HTML code is Off Forum Rules

All times are GMT +8. The time now is 07:40.

 Aaron's homepage - Top