Writeup JHDigitalCTF (John Hammond Digital CTF) 2019 Kategori [Crypto]
Sunday, 10 November 2019 | est. 1 min read |
Tags :
#ctf
#jhdctf
#cryptography
Executive Order
70
I found this weird file a bit ago... I've tried to operate with it but I can't seem to get it to work. I've tried the whole range of possibilities!
Download the file below.
file : prompt.txt
the file contain hex-decoded string, i think its a flag, but after we try to decode it to ascii, it doenst show a readble string. so in this case we try to check the first hex character and XOR it with i while i in range (0,300) and than we found the first char is decoded to "J" if xored with 239.
a = [0xa5,0xa7,0xab,0xac,0xbb,0xa9,0x94,0x98,0x87,0x8a,0x81,0xb0,0x86,0x81,0xb0,0x8b,0x80,0x9a,0x8d,0x9b,0xb0,0x97,0x80,0x9d,0xb0,0x86,0x9b,0xb0,0x80,0x9a,0x9b,0x92]
for i in a:
print(chr(i ^ 239),end="")
Flag = JHDCTF{when_in_doubt_xor_it_out}