TL;DR Walkthrough of Introduction to Cryptography, part of TryHackMe’s new Security Engineer pathway.
A full list of our TryHackMe walkthroughs and cheatsheets is here.
The Security Engineer pathway is new to TryHackMe, so Google isn’t already flooded with walkthroughs of the room. Hence I figured I’d post my notes in case it helps anyone else.
On a sidenote, TryHackMe’s promotion of the new Security Engineer pathway ended 25 September. I was in training for work during most of the promotion and hence only got a few rooms done. I did not win anything via the tickets. Hopefully one of you did.
This room can be done completely in BASH in Kali, all I had to do was run updates and add hmac256 to Kali.
I am going to assume that everyone reading this already knows what PKI is, has digitally signed and encrypted email before, and knows about hashes and how passwords are stored. Hence we will just plough ahead into how to get the answers using a standard issue Kali VM.
— — Task 2 — -
Decrypt the file quote01 encrypted (using AES256) with the key s!kR3T55 using gpg. What is the third word in the file?
gpg - output origninal_message.txt - decrypt quote01.txt.gpg
Do not waste time idling or thinking after you have set your goals.
Decrypt the file quote02 encrypted (using AES256-CBC) with the key s!kR3T55 using openssl. What is the third word in the file?
openssl aes-256-cbc -d -in quote02 -out original_message2.txt
The true science of martial arts means practicing them in such a way that they will be useful at any time, and to teach them in such a way that they will be useful in all things.
Decrypt the file quote03 encrypted (using CAMELLIA256) with the key s!kR3T55 using gpg. What is the third word in the file?
gpg — output origninal_message3.txt — decrypt quote03.txt.gpg
You must understand that there is more than one path to the top of the mountain.
— — Task 3 — -
Bob has received the file ciphertext_message sent to him from Alice. You can find the key you need in the same folder. What is the first word of the original plaintext?
openssl pkeyutl -decrypt -in ciphertext_message -inkey private-key-bob.pem -out decrypted.txt
“Perception is strong and sight weak. In strategy it is important to see distant things as if they were close and to take a distanced view of close things.”
Take a look at Bob’s private RSA key. What is the last byte of p?
openssl rsa -in private-key-bob.pem -text -noout
First prime #, last 2 digits
Take a look at Bob’s private RSA key. What is the last byte of q?
Second prime #, last 2 digits
— — Task 4 — -
A set of Diffie-Hellman parameters can be found in the file dhparam.pem. What is the size of the prime number in bits?
openssl dhparam -in dhparams.pem -text -noout
What is the prime number’s last byte (least significant byte)?
— — Task 5 — -
What is the SHA256 checksum of the file order.json?
Open the file order.json and change the amount from 1000 to 9000. What is the new SHA256 checksum?
I simply used gedit to change it.
Using SHA256 and the key 3RfDFz82, what is the HMAC of order.txt?
sudo apt-get update
yes to all
hmac256 3RfDFz82 order.txt
— — Task 6 — -
What is the size of the public key in bits?
openssl x509 -in cert.pem -text
Till which year is this certificate valid?
— — Task 7 — -
You were auditing a system when you discovered that the MD5 hash of the admin password is 3fc0a7acf087f549ac2b266baf94b8b1. What is the original password?
hashcat -m 0 “3fc0a7acf087f549ac2b266baf94b8b1” /home/kali/Downloads/Wordlists/rockyou.txt
An alternate method is to simply copy/paste the hash into crackstation.net
I’m always happy to see TryHackMe roll out a new pathway. This one has been educational and interesting so far. It’s unfortunate that I was unable to get more rooms done during the promotion due to work and life. My co-worker didn’t join, so I couldn’t get tickets for referrals. TryHackMe didn’t like my last walkthrough on Active Directory Hardening, so no tickets there. Hopefully ya’ll won something even though I didn’t!