picoCTF 2024 Blast from the past Challenge solve

In this write-up , i will show you how did i solve Blast from the past challenge from picoCTF 2024.

Challenge Description:

The judge for these pictures is a real fan of antiques. Can you age this photo to the specifications?Set the timestamps on this picture to 1970:01:01 00:00:00.001+00:00 with as much precision as possible for each timestamp. In this example, +00:00 is a timezone adjustment. Any timezone is acceptable as long as the time is equivalent. As an example, this timestamp is acceptable as well: 1969:12:31 19:00:00.001-05:00. For timestamps without a timezone adjustment, put them in GMT time (+00:00). The checker program provides the timestamp needed for each.

Use this picture.

so after i downloaded the the given picture i used exiftool and i have noticed there is some timestamps

Modify Date

Date Original // Create Date

Time stamp ?? (This is important)

so yeah let’s change all dates to 1970:01:01 00:00:00.001+00:00 with exiftool

exiftool -AllDates='1970:01:01 00:00:00.001' -CreateDate='1970:01:01 00:00:00.001' -DateTimeOriginal='1970:01:01 00:00:00.001' -ModifyDate='1970:01:01 00:00:00.001' -SubSecCreateDate='1970:01:01 00:00:00.001' -SubSecDateTimeOriginal='1970:01:01 00:00:00.001' -SubSecModifyDate='1970:01:01 00:00:00.001' original.jpg

this command will change all the dates to what we want let’s try to upload it

nc -w 2 mimas.picoctf.net 55107 < original.jpg
nc mimas.picoctf.net 59807

hmmmm Samsung:TimeStamp ???

so the challenge have started , after some search i found that the Time Stamp that we got in the exif tool is the Samsung:TimeStamp so now let’s edit with exiftool….we can’t.

so after some search again i used strings original.jpg and i have found this

i have found it so now what is this number ? 1700513181420

it’s this date 2023:11:20 15:46:21.420–05:00 but in milisec unix timestamp

so it’s easy now we will convert 1970:01:01 00:00:00.001+00:00 to unix timestamp and replace it

so i used website called Unix Time Stamp — Epoch Converter

i put the date i want then clicked convert and this was the output

0 yeah it’s 0 so now we want to replace the 0 with our old date so i used hexeditor i opened it then CTRL + W then chose search for text string

then search for UTC to quickly go to the data we want to edit

HEX

ASCII

so let’s replace the numbers that after Data to replace it let’s begin after 74 61 from 31 so to write 0 in hex we write 30 and if we want to delete a value we put 00

HEX

ASCII

CTRL + X to exit and save

now there is a problem

it’s all 00000000 ? so after some search i have figuered that we need to put it in milisecs not in seconds so it will be 00001 and this one for the 00:00:00.001 so let’s edit the hex again so we will start after the 74 61 and let’s write 30 30 30 30 31

let’s save and send it to the server

Following these steps should help you successfully complete the challenge.