GryphonCTF_2016: Sanity Crypto

Category: Sanity Points: 5 Description:

Creator - Darren Ang (@txsouth)

Write-up

We are given a string,

MDEwMDAxMTEgMDEwMDAwMTEgMDEwMTAxMDAgMDEwMDAxMTAgMDExMTEwMTEgMDAxMTAxMTAgMDAxMTAwMDEgMDExMTAxMTAgMDAxMTAwMTEgMDAxMTAxMDAgMDExMTAxMTEgMDAxMTAxMDAgMDExMTEwMDEgMDEwMTExMTEgMDExMTAwMDAgMDAxMTAwMDAgMDAxMTAwMDEgMDExMDExMTAgMDAxMTAxMTEgMDAxMTAxMDEgMDEwMTExMTEgMDAxMTAxMDAgMDExMTAwMTAgMDAxMTAwMTEgMDEwMTExMTEgMDAxMTAxMTAgMDExMTAwMTAgMDAxMTEwMDAgMDExMTExMDE=

The equals at the back tell us this is probably base64. Using a base64 -> string, we get

01000111 01000011 01010100 01000110 01111011 00110110 00110001 01110110 00110011 00110100 01110111 00110100 01111001 01011111 01110000 00110000 00110001 01101110 00110111 00110101 01011111 00110100 01110010 00110011 01011111 00110110 01110010 00111000 01111101

Which, of course is binary. Putting that through a binary -> ascii converter, we get

GCTF{61v34w4y_p01n75_4r3_6r8}

Therefore, the flag is GCTF{61v34w4y_p01n75_4r3_6r8}.