AES Encryption

AES-GCM (Galois/Counter Mode) is authenticated encryption — it not only encrypts your data but also generates an authentication tag that detects any tampering with the ciphertext. If even one byte of the encrypted output is modified, decryption fails with an error. AES-CBC (Cipher Block Chaining) is older and encrypts correctly but does not authenticate — an attacker can modify the ciphertext in certain ways without detection. Use GCM for all new implementations. Only use CBC if you need compatibility with a specific legacy system that requires it.

PBKDF2 (Password-Based Key Derivation Function 2) converts your human-readable password into a cryptographic key. It runs the password and a random salt through SHA-256 hashing 100,000 times. This deliberate slowness means that brute-forcing a weak password like "password123" still requires running 100,000 SHA-256 iterations per guess attempt — dramatically reducing the attack speed compared to simply hashing once. The random salt ensures that two users with the same password get completely different keys.

The output is a single Base64-encoded string that packages everything needed for decryption: the random salt (used by PBKDF2 to derive the key), the IV (Initialization Vector, a random nonce required by GCM/CBC), the encryption mode and key size identifier, and the actual ciphertext. This self-contained format means the recipient only needs the password — the output string alone is safe to share publicly since none of the included data compromises the encryption.

Yes. The output format is documented: Base64-decode the string, then extract the salt (first 16 bytes), IV (next 12 bytes for GCM or 16 for CBC), and remaining ciphertext. Run PBKDF2 with SHA-256 and 100,000 iterations on the password and salt to get the key, then decrypt with AES-GCM or AES-CBC. The Web Crypto API (browser), crypto module (Node.js), PyCryptodome (Python), and javax.crypto (Java) all support these algorithms natively.

With AES-GCM, decryption will fail immediately with an authentication error because the authentication tag will not match. This is one of the key advantages of GCM — it tells you definitively that decryption failed rather than silently producing garbage output. With AES-CBC, wrong password decryption produces garbled output without an obvious error, making it harder to detect. In both cases, the original data is not recoverable without the correct password.

AES-256 (256-bit keys) is the recommended choice for new implementations. The key length difference is meaningful in theory — AES-128 has 2^128 possible keys while AES-256 has 2^256. In practice, both are computationally unbreakable with current technology, but AES-256 provides a larger security margin against theoretical future attacks. The performance difference is negligible for text encryption. Use 128-bit only if you have a specific compatibility requirement.

Nothing is sent to any server. All encryption and decryption runs in your browser using the Web Crypto API, a native browser API that provides cryptographic operations in a secure, sandboxed environment. Your plaintext, your password, and your ciphertext never leave your device. This makes the tool safe for encrypting sensitive credentials, personal messages, and confidential data.