Delta

##Challenge Name: Delta

###Solves

• >Solves: 69
• >Points: 387

###Description

A cryptic data file has surfaced, carrying hidden information that once belonged elsewhere. Only by understanding its origin can you recover the secret it holds. Will you be able to decipher its true meaning and uncover the flag?

File provided:

###Approach

Upon extracting delta.zip, we were provided with two files: null.bmp and flag.bin.

1. >

   Identifying the Flag Binary: We ran the

   file

   command on flag.bin and found that it was a VCDIFF binary file. This suggested that it was intended to be used for a binary diffing or patching operation.

2. >

   Examining the BMP File: Opening null.bmp showed that it did not contain the flag, implying that the file needed modification or patching using flag.bin.

   

3. >

   Merging the Files: We used xdelta3, a tool designed to handle VCDIFF patches, to merge the two files. The following command was used:

   bash

   xdelta3 -d -s null.bmp flag.bin output.bmp

   This command applied the patch from flag.bin to null.bmp, resulting in a new image file: output.bmp.

   

4. >

   Revealing the Flag: Opening output.bmp revealed the hidden flag.

Flag:

EKO{b3st_d3lt4}