Tools / AES Decryptor
Decrypt AES ciphertexts when you already have the key. Supports the four common modes, accepts hex / base64 / UTF-8 inputs for each field, and shows the plaintext as UTF-8, hex, and base64 simultaneously. Built on the browser’s Web Crypto API; nothing is sent to a server.
WebCrypto AES-CBC always removes PKCS#7 padding (and rejects invalid padding). This toggle only affects ECB.
Common mistakes: wrong IV format (hex vs base64), wrong key length (32 hex chars = 16 bytes = AES-128), and forgetting that AES-GCM needs the auth tag concatenated to the ciphertext. If the decrypt errors with OperationError the most likely culprits are key length, IV length, or a corrupted ciphertext.
For challenges where you do not have the key, you may need to attack the cipher construction: padding oracles for AES-CBC, IV reuse / nonce reuse for GCM, repeated-block analysis for ECB. The dedicated decrypt tools complement (rather than replace) the XOR Cipher and RSA Calculator for asymmetric setups.