Writeup of 0000 stage of Google CTF Beginners Quest 2023
What is Google CTF?
Google will run the 2023 CTF competition in two parts: an online jeopardy-CTF competition, and a different on-site contest open only to the top 8 teams of the online jeopardy-CTF competition. "Capture The Flag" (CTF) competitions are not related to running outdoors or playing first-person shooters. Instead, they consist of a set of computer security puzzles (or challenges) involving reverse-engineering, memory corruption, cryptography, web technologies, and more. When players solve them they get a "flag", a secret string which can be exchanged for points. The more points a team earns, the higher up it moves in rank.
Introduction:
Julius Caesar used the Caesar cipher to send secret messages to his generals during his military campaigns. The cipher is a simple substitution cipher that shifts each letter of the alphabet by a certain number of positions. Caesar used a shift of three, so each letter in his messages was replaced by the letter three positions to its right in the alphabet. For example, the letter "A" would be replaced by the letter "D," the letter "B" would be replaced by the letter "E," and so on.
Caesar's generals knew the shift value, so they could easily decrypt the messages. However, the cipher was still effective at protecting Caesar's messages from his enemies, who did not know the shift value.
Caesar's use of the cipher is first described by Suetonius in his biography of Caesar. Suetonius writes that Caesar used the cipher to send messages to his generals during the Gallic Wars. He also writes that Caesar used the cipher to send messages to the Roman Senate while he was fighting in the Civil War.
The Caesar cipher is a relatively simple cipher, and it can be easily broken by modern cryptanalysis techniques. However, it was an effective cipher in
Caesar's time, and it helped him to keep his military communications secret.
Challenge 0:
Let's test your knowledge on Caesar's methods
Challenge 1
This one is not exactly Caesar but it might be the key
Challenge 2:
We use our alphabet too frequently, let's try an alternative one
Challenge 3:
This tricky one introduces transposition
Timestamps:
00:00 - Start
00:13 - Challenge 0
00:44 - Challenge 1
01:35 - Challenge 2
03:05 - Challenge 3
#googlectf #beginnerschallenge #googlectf2023
