decryptText function
Implementation
String decryptText(String base64Text, String keyText, String ivText) {
keyText = sha512(dart_convert.utf8.encode(keyText)).substring(0, 32);
ivText = sha512(dart_convert.utf8.encode(ivText)).substring(0, 16);
final key = encrypt_encrypt.Key.fromUtf8(keyText);
final iv = encrypt_encrypt.IV.fromUtf8(ivText);
final encrypter = encrypt_encrypt.Encrypter(encrypt_encrypt.AES(key));
return encrypter.decrypt64(base64Text, iv: iv);
}