Archived Challenges - June 2024

/shrug

ictf{welcome_to_mini_round_47!}

Known plaintext attack on XOR. Cyberchef solve: From Hex → XOR → Use key ictf{ and you get 13371 meaning the key is 1337 and is being repeated. Just XOR with 1337 to get the flag!

ictf{jus7_gu3ss_7h3_k3y}

Just undo the bitwise operations. The first operation to undo is the left shift (<<) and can be undo-ed by right shift (>>). To undo the NOT operator (~), do the NOT operation again. In the end, XOR by 5.

ictf{1_4m_4_b1t_w1s3}

Actually undo the bitwise operations. First XOR by NOT of 9. Then right shift by 7. Finally, do the NOT operator.

ictf{guess_1_4m_n0t_a_bit_wise}

Two pure functions are provided, one to XOR a given character with 0x007 and one to rotate a bit right once. One impure function is provided that stores the result in storage of the result of the functionals at the right of it, and loading the next flag character for the functionals at the left for processing. It's easier to crack since the source code is provided, but reversing a binary will be annoying due to the involvement of the stack. Maybe next time.

ictf{7h15_wa5_a_m157ak3_a1b2c3d4}

Easy way: run strings and the flag is in plaintext. Preferable way: open a decompiler and familiarize yourself with the process.

ictf{b3g1nn3r_crackm3_21k7f3ml5}

Notice that least significant bit layers of each of the colours (R, G, B) do not look like they belong to the image. Overlay them to reveal a QR code. As the image is probably too noisy to be scanned by a QR code reader, replace every block that shouldn't be black to consist only of white pixels. Now scan the QR code to get the flag.

ictf{1_d0nt_kn0w_wh4t_t0_put_h3r3_h4v3_4_n1c3_d4y_1_gu3ss}

Hash all the 3 letter combinations, keep making requests to /characters until you've seen every index

https://cybersharing.net/s/cfe422b58bb223f0

ictf{00ps_th1s_1s_jus7_l0ts_0f_thr33_l3tt3r_p4ssw0rds}