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Security
AES CBC Mode Decryption Without IV
Problem AnalysisFirst, examine the request and find that the password is encryptedFollowing the code, discover it's AES encryption in CBC mode. The ciphertext is sent to the server, and the key is stored in the session. However, there's no IV (initialization vector).With only the key, the random IV only affects the first 64 bits of the result. You can see that 64 random characters are generated.Conclusion In AES CBC mode, if there's no IV (initialization vector), data can still be decrypted as long as you have the key. The IV's purpose is to ensure that identical plaintext produces different ciphertext in different encryption processes. Without an IV, using an all-zero IV for decryption works correctly.