Hacker101 Encrypted Pastebin

Encryption protects confidentiality, not integrity.

"title":"test","body":"test","flag":"^FLAG^[REDACTED]$FLAG$"

The second flag is where the challenge becomes truly educational—and demanding. After creating a legitimate pastebin, participants must copy the base64post argument from the generated URL and then exploit a to decipher the encrypted message. hacker101 encrypted pastebin

While not inherently broken, CBC is difficult to implement securely against padding oracles. 6. Conclusion

: Essential for automating the decryption and encryption process. Encryption protects confidentiality, not integrity

The application allows you to create "encrypted" pastes. When you view a paste, the URL contains a base64-encoded ciphertext in a parameter like post= . By altering a single byte of this ciphertext and reloading the page, you can observe different server behaviors: The page loads (likely with garbled data).

The Encrypted Pastebin is a CTF challenge presented as a web application that purports to be "the most secure pastebin on the internet." The site claims to use AES-128 encryption, assuring users that their data is safe because the key is never stored in the database. While not inherently broken, CBC is difficult to

When the Encrypted Pastebin receives a modified ciphertext, it attempts to decrypt it and validate the PKCS#7 padding. If the padding is structurally incorrect, it throws a "Padding Error." If the padding is correct but the resulting plaintext is gibberish, it throws a different error or handles the request normally. This subtle distinction in responses is the "oracle" that an attacker can exploit. The Cryptography Behind the Exploit In CBC mode, each plaintext block ( Picap P sub i ) is generated by XORing the decrypted ciphertext block ( ) with the previous ciphertext block ( Ci−1cap C sub i minus 1 end-sub