Encryption Without Integrity: How CBC Bit Flipping Exposes Data to Tampering

The CBC bit flipping attack exposes a critical misconception in cryptography: encryption protects confidentiality but not integrity, allowing attackers to modify encrypted data without ever knowing the secret key. This vulnerability has devastating real-world consequences, as demonstrated by session cookie exploits that enable privilege escalation despite full encryption. For developers, this distinction is fundamental—it underscores why modern systems require authenticated encryption that guarantees both confidentiality and data integrity.