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substitution1

  • Description: A second message has come in the mail, and it seems almost identical to the first one. Maybe the same thing will work again.
  • Difficulty: Medium

🔎 Solution​

Similar to the substitution0 challenge, the provided text is also encrypted with a substitution cipher.

Using an online tool to automatically decrypt it, we obtain the substitution key as ATZMXDREBLNJIVQCOFGWPYHUSK.

The original message is then decrypted as follows:

CTFS (SHORT FOR CAPTURE THE FLAG) ARE A TYPE OF COMPUTER SECURITY COMPETITION. 
CONTESTANTS ARE PRESENTED WITH A SET OF CHALLENGES WHICH TEST THEIR CREATIVITY, TECHNICAL (AND GOOGLING) SKILLS, AND PROBLEM-SOLVING ABILITY. 
CHALLENGES USUALLY COVER A NUMBER OF CATEGORIES, AND WHEN SOLVED, EACH YIELDS A STRING (CALLED A FLAG) WHICH IS SUBMITTED TO AN ONLINE SCORING SERVICE. 
CTFS ARE A GREAT WAY TO LEARN A WIDE ARRAY OF COMPUTER SECURITY SKILLS IN A SAFE, LEGAL ENVIRONMENT, AND ARE HOSTED AND PLAYED BY MANY SECURITY GROUPS AROUND THE WORLD FOR FUN AND PRACTICE. 

FOR THIS PROBLEM, THE FLAG IS: PICOCTF{FR3QU3NCY_4774CK5_4R3_C001_4871E6FB}

🚩Flag​

picCTF{FR3QU3NCY_4774CK5_4R3_C001_4871E6FB}