TFC-CTF Write-up(c-c-c)

how noob am i?

REVERSE

SIGNAL

check it with DIE,64 bit

step into the main func,nothing sus here,lets check the function list

we can find some very sussy name here

check the function GenerateChallenge,seems like the flag is a random string within”a” to “9”

now it is clear, check the other functions

and this is the flag

TFCCTF{b11e807f65b27dcf82e70c4bad63a3eb}

CRYPTO

CCCCC

5c4c4c6c4c3c4c3c5c4c4c6c7cbc6c3c7c3c6c8c6cfc7c5c7c4c5cfc6c3c6cfc7c5c7c4c5cfc6c3c7c4c3c0c5cfc6c3c6cdc7c9c5cfc6c3c6c2c3c0c7c9c5cfc6c3c3c4c6cec6c4c5cfc6c3c6cdc7c9c5cfc6c3c6c4c6cfc6c7c5cfc6c3c6c1c6cec6c4c5cfc6c3c6cdc7c9c5cfc6c3c6c3c3c4c3c7c7cdc0ca
​

remove all letter C from the text

then 16bytes|ASCII chara

5446434354467b6373686f75745f636f75745f6374305f636d795f636230795f63346e645f636d795f63646f675f63616e645f636d795f636334377d0a
​

TFCCTF{cshout_cout_ct0_cmy_cb0y_c4nd_cmy_cdog_cand_cmy_cc47}

GENETICS

CCCA CACG CAAT CAAT CCCA CACG CTGT ATAC CCTT CTCT ATAC CGTA CGTA CCTT CGCT ATAT CTCA CCTT CTCA CGGA ATAC CTAT CCTT ATCA CTAT CCTT ATCA CCTT CTCA ATCA CTCA CTCA ATAA ATAA CCTT CCCG ATAT CTAG CTGC CCTT CTAT ATAA ATAA CGTG CTTC

The correspondence can be found clearly:

CCCA->T

CACG->F

CAAT->C

CAAT->C

CCCA->T

CACG->F

From this correspondence,we can infer that the basic group A,T,C,G matches correspond to 2,1,3,0

(Special Thanks:G3rling)

therefore:

Letter	Quaternary Code	Nucleotide
A	3213	CATC
B	3220	CAAG
C	3221	CAAT
D	3222	CAAA
E	3223	CAAC
F	3230	CACG
G	3231	CACT
H	3232	CACA
I	3233	CACC
J	3300	CCGG
K	3301	CCGT
L	3302	CCGA
M	3303	CCGC
N	3310	CCTg
O	3311	CCTT
P	3312	CCTA
Q	3313	CCTc
R	3320	CCAG
S	3321	CCAT
T	3322	CCAA
U	3323	CCAC
V	3330	CCCg
W	3331	CCCt
X	3332	CCCA
Y	3333	CCCC
Z	0000	GGGG

and punctuation matches their position in the ASCII code tb.

the flag:

TFCCTF{1_w1ll_g3t_th1s_4s_4_t4tt00_V3ry_s00n}