Hardware

Serial Logs:

Solved by : Nigamelastic

• .sal files are saleae logic analyzer files.
• I got this as reference https://dystopia.sg/allesctf20-PWNkemon/ so i downloaded the sla logic analyzer https://www.saleae.com/downloads/
• from here after installing, i opened the sal files which i could and then the following:
• I imported the value i am pretty sure if i find the right analyzer it should work

• by far for this challenge async serial works the best
• challenge states raspberry pi which has a baud rate of 115200
• after some pondering i realized that there are some errors in parity on fixing them and using the 115200 in async serial we get the hex converting which gives us this:

https://www.dropbox.com/s/ztqoa16wvp6rvf6/message.txt?dl=0

• found this : https://6e726d.github.io/Challenge/Ekoparty15/
• this writeup explains how to get the baud rate
• open the SAL file and zoom

• zoom

• zoom

• zoom

• until you see the smallest unit of the digital wave then measure it: as its 13.498

• since it is in μ we will divide it by 1000000
• so 1000000/13.498 = 74085.049637
• I obviously used 74000 as bit rate, converted the hex to ascii with the tool itself and it gave me the flag:

CHTB{wh47?!_f23qu3ncy_h0pp1n9_1n_4_532141_p2070c01?!!!52}

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Compromised

Solved by : Nigamelastic

• import the file in salea logic analyzer, and use i2c analyzer
• export the data and you will see two columns if we take everything written and try the hex dump we get

set_maCxH_lTimB{itn_tuo1:110_se73t_2mimn1_nli4mi70t_2to5:_1c0+.]<+/4~nr^_yz82Gb3b"4#kU_..4+J_5.

3M.2B1.4B.1dV_5. yS.5B7k3..1V.Qxm.!j.@Q52yq)t%# @5%md}S.

• and we can see its slightly off i noticed the following :

• so i used only 0x2C used the corresponding hex

which is

0x43 0x48 0x54 0x42 0x7B 0x6E 0x75 0x31 0x31 0x5F 0x37 0x33 0x32 0x6D 0x31 0x6E 0x34 0x37 0x30 0x32 0x35 0x5F 0x63 0x34 0x6E 0x5F 0x38 0x32 0x33 0x34 0x6B 0x5F 0x34 0x5F 0x35 0x33 0x32 0x31 0x34 0x31 0x5F 0x35 0x79 0x35 0x37 0x33 0x6D 0x21 0x40 0x35 0x32 0x29 0x23 0x40 0x25 0x7D

• and got the flag

CHTB{nu11_732m1n47025_c4n_8234k_4_532141_5y573m!@52)#@%}