For some reason my code give m a error for when i try and grab the byte from this section. and i don't know what the problem is. static byte[] encryptstringtobytes_aes(string plaintext, byte[] key) { byte[] encrypted; byte[] iv; using (aes aesalg = aes. { aesalg. key = key; aesalg. generateiv(); iv = aesalg. iv; aesalg. mode = ciphermode. cbc; var encryptor = aesalg. createencryptor(aesalg. key, aesalg. iv); // create the streams used for encryption. using (var msencrypt = new { using (var csencrypt = new cryptostream(msencrypt, encryptor, cryptostreammode. write)) { using (var swencrypt = new streamwriter(csencrypt)) { //write all data to the stream. swencrypt. write(plaintext); } encrypted = msencrypt. toarray(); } } } var combinedivct = new byte[iv. length + encrypted. length]; array. copy(iv, 0, combinedivct, 0, iv. length); array. copy(encrypted, 0, combinedivct, iv. length, encrypted. length); // return the encrypted bytes from the memory stream. return combinedivct;