Decrypt given data previously encoded with rc4-40 cipher algo. RC4 with a 40-bit key size, providing weak encryption and typically used in environments with strict export restrictions. RC4-40 was a variant used under encryption export restrictions, offering very weak security. RC4-40 is extremely insecure and vulnerable to modern attacks, and its use is strongly discouraged. Our decryption process assumes the IV string is prepended in the encoded string during the encryption process. You can not decrypt and get the correct results if the IV or passphrase mismatch occurs between encryption and decryption process.