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🔐 Ciphers & Codes

Secret messages have been scrambled using different cipher techniques. Use the reference tools below each challenge to decode them. Flags are always agent{decoded-word}.

0/6 solved · 0/120 pts

🔄 Caesar Shift Tool

Plain:

Cipher:

Shift:

Top row = original letter. Bottom row = encoded letter at this shift.

📡 Morse Code Reference

🔲 Pigpen Cipher Key

Grid 1 — Letters A to I (no dot)

Each shape shows the lines between cells. The letter label tells you which letter each shape represents.

Grid 2 — Letters J to R (with dot •)

X Shapes — S to Z

Julius Caesar used to send secret messages by shifting every letter forward by 3. So A became D, B became E, and so on.

This message was encoded with a shift of 3. Use the Caesar Shift Tool above (set to shift 3) to decode it:

DJHQW{VKLIW-WKUHH}

The decoded message is the flag. Enter it below (it will start with agent{).

Set the shift tool to 3. For each letter in the coded message, find it in the bottom row (Cipher), and read the letter above it in the top row (Plain). For example, D in cipher → A in plain.

✓ Cracked! Caesar ciphers are easy to break when you know the shift. Even without knowing it, there are only 25 shifts to try!

Sometimes secret messages are simply written backwards. Can you read this one?

}reverse{tnega

Read it from right to left to decode the flag. Enter it below.

Read each character from the RIGHT side to the LEFT side. The last character } becomes the first, and so on. The decoded message starts with agent.

✓ Reversed! Notice that "esrever" spells "reverse" backwards — a hidden joke in the flag itself.

The Pigpen cipher was used by Freemasons in the 1700s to keep their communications secret. Each letter is replaced by the shape of the "pen" it sits in from the key diagrams above.

Decode this Pigpen message using the key above. The symbols spell out two words separated by a hyphen:

Use the Pigpen Key above to match each symbol to its letter. The flag is agent{first-word-second-word}.

Look at the shape of each symbol and find the matching shape in the Pigpen Key grids. A dot in the shape means it's from Grid 2 (J–R). Count symbols: there are 11 (6 before the dash, 4 after).

The first letter P is from the dotted grid (bottom-left cell). The decoded message spells out the name of the cipher you're using right now!

✓ Decoded the Pigpen! This cipher was used by secret societies for hundreds of years.

This message was encoded with a Caesar cipher — but we don't know the shift! You'll need to try different shifts using the tool above until you get a real English word inside the agent{} brackets.

HNLUA{MYLXBLUJF}

Use the Caesar Shift Tool above. Try different shift values until the letters inside the brackets spell a real English word. There are only 25 possible shifts — be systematic!

Try each shift from 1 to 25. At each shift, decode all the letters in the message. You'll know you found the right shift when the part inside {} spells a real English word.

The shift is a single digit (less than 10). The word inside the brackets is related to how code-breakers work out what shift was used — they analyse how often each letter appears.

✓ You found the shift! Real code-breakers use frequency analysis — E is the most common letter in English, so the most common letter in the ciphertext is probably E.

Morse code was used to send messages by telegraph — tapping short and long signals. A dot (•) is a short tap, a dash (—) is a long tap.

Decode this Morse message using the reference chart above. Each group of dots/dashes is one letter. The slash (/) marks the boundary between words in the flag:

The decoded flag uses hyphens between the three words: agent{word1-word2-word3}

Decode each group of dots and dashes using the Morse Reference chart above. The three groups separated by / form three words. Combine them with hyphens to make the flag.

The three groups (before, between, and after the two / separators) decode to words of 4 letters, 3 letters, and 6 letters. Start with the shortest group — it's only 3 symbols — and look it up in the reference chart.

✓ Dit-dah! Morse code is still used today — pilots learn it as part of their training.

In this cipher, each letter has been replaced by a number. The numbers are NOT in order (it's not A=1, B=2 — that would be too easy!). You've been given most of the key, but a few entries are missing — you'll need to figure those out from the encoded message.

Partial Key (known letters):

Encoded message:

12 - ? - 3 - 12 - 17 - 5 - 19 / 12 - 8 - 19 - 5

The ? represents an unknown letter (r=11 and k=17 are missing from the key). Work out what letters fit to make a real word. The flag is agent{word1-word2} (first word slash second word).

The second word "12-8-19-5" decodes to c-o-d-e = "code". The first word has the pattern c-?-a-c-?-e-d. What 7-letter word meaning "broken/solved" fits? Think about what a code-breaker does.

The second word is already fully decodable (all its numbers are in the key). Once you know the second word, think about what a spy or code-breaker would say they've done to a secret message. The first word follows the pattern c _ a c _ e d.

✓ You cracked the code! Real substitution ciphers can have any scrambled alphabet — but context and word patterns always give them away.