Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsFor picoCTF’s Vault Door Training, open VaultDoorTraining.java and inspect checkPassword(). The comparison there reveals the password directly; compiling or running the program is not necessary. Use the literal from your own challenge file, then place it inside picoCTF{...} to form the flag.
Find the password in the source
- Open
VaultDoorTraining.javain a text editor. - Search the file for
checkPassword. - In that method, locate the string literal compared with the supplied password. That literal is the value the check accepts.
The challenge’s source comment asks whether it is safe to put a password in source code. The exercise’s answer is demonstrated by the code itself: anyone who can read the source can see a secret stored there. A community writeup identifies the Java file and its source-reading hint in its Vault Door writeup.
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Why the literal becomes the flag
In main(), the program reads an input token, removes the picoCTF{ prefix and the final character, and passes what remains to checkPassword(). That means the compared literal is the flag content, not the complete flag. Once you have verified the value in your file, wrap it as picoCTF{literal}, replacing literal with the exact text you found. The input handling is also described in this public Java source copy and a picoGym walkthrough.
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Do not rely on a flag copied from an unrelated walkthrough. Public copies cited in community material show different password literals, and the available sources do not establish which literal matches every copy of the challenge. Read the comparison string in the exact VaultDoorTraining.java file you received and use that value. A historical walkthrough also records a different literal: picoCTF 2019 Reverse Engineering.
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Do you need to compile or run it?
No. Static inspection is enough to discover the accepted string. Running the program can serve as an optional confirmation if you already have a Java environment, but it adds setup and is not needed to solve this challenge. A Vault Door Training walkthrough likewise notes that the comparison string is visible in the source.
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