AES Encrypt/Decrypt

AES (Advanced Encryption Standard) is the most widely used symmetric encryption algorithm. It was established by NIST in 2001 and is used worldwide to protect classified information, secure web traffic (TLS), encrypt files and protect databases. AES uses the same key for encryption and decryption — symmetric encryption. This tool derives a 128, 192 or 256-bit key from your passphrase using PBKDF2-SHA256 with a random per-message salt.

The number refers to the key length in bits. AES-256 uses a 256-bit key (32 bytes) and provides the largest security margin; AES-192 uses 24 bytes and AES-128 uses 16 bytes. All three are considered secure against classical attacks today. AES-256 is the most conservative choice against future quantum attacks (Grover's algorithm halves the effective key length, leaving AES-256 with a 128-bit margin). AES-128 is slightly faster and is sufficient for most applications.

Use AES-GCM whenever you can. GCM is an authenticated (AEAD) mode: it produces an authentication tag alongside the ciphertext, so tampering or a wrong key is detected reliably and decryption fails loudly. AES-CBC only provides confidentiality — it detects neither tampering nor a wrong key, so a wrong passphrase usually yields garbage output instead of an error. CBC is offered only for compatibility with older systems and libraries (for example CryptoJS defaults). If you must use CBC, authenticate the ciphertext separately with an HMAC.

Your passphrase is stretched with PBKDF2-HMAC-SHA256 using a fresh 16-byte random salt generated for every encryption, and 250,000 iterations by default (you can raise this to 600,000 or 1,000,000). Because the salt is random per message, the same passphrase produces a different key every time, which defeats precomputed rainbow tables. The salt is stored in the output so decryption can reproduce the key. Note that PBKDF2 protects against brute-force, but a weak passphrase is still weak — use a long random key, or generate one with the "Generate" button.

This tool uses the Web Crypto API (crypto.subtle), which provides native, hardware-accelerated AES in the browser, and the cryptography itself is sound. All processing happens locally — nothing is sent to a server. However, browser-based encryption has inherent risks: your key sits in memory, the page could be compromised by XSS, and malicious browser extensions could intercept data. For truly sensitive data, use a dedicated encryption application rather than a web tool.

Only if the other tool uses the exact same construction. This tool packs salt, IV, algorithm parameters and ciphertext into one binary blob and Base64/Hex encodes it — that layout is specific to this page. Standard OpenSSL "enc" output starts with the bytes "Salted__" and uses a different KDF (or MD5 in legacy mode), so it will not decrypt here. If you need cross-tool compatibility, use a command-line tool such as OpenSSL where you control every parameter explicitly.