An IV is not a key, it just changes the state of the block chain and must
the same size as the block. The key can be a different size than the block,
the IV can not in this case. Your program complains because you are reusing
the key as an IV, and this key-IV happens to be a different size than the
block.
You shouldn't create the IV this way. The IV is supposed to be public,
randomly generated, and shouldn't be reused.
If you don't want to use an IV, set it to a block of zeroes and then
encrypt one random block of data before encrypting your plaintext. This
randomizes the blockchain. When the decryptor receives the first
ciphertext, he can decrypt the first block and then discard it.
There is no need to base64 encode your data, it doesn't add anything in
terms of secrecy.
Consider AES-GCM for authenticated encryption in your next project.
On Wednesday, June 29, 2016 at 11:57:11 PM UTC-7, Lazytiger wrote:
>
> Hi, all
>
> I have a C# code to decrypt data as following
>
> public static string test(string input, string key)
> {
> if (((input == null) || string.IsNullOrEmpty(input.Trim()))
> || ((input == "false") || (input == "null")))
> {
> return string.Empty;
> }
> RijndaelManaged managed = new RijndaelManaged {
> KeySize = 0x100,
> BlockSize = 0x100,
> Mode = CipherMode.CBC,
> Padding = PaddingMode.PKCS7,
> Key = Encoding.ASCII.GetBytes(key),
> IV = Encoding.ASCII.GetBytes(key)
> };
> try
> {
> byte[] buffer = Convert.FromBase64String(input);
> ICryptoTransform transform = managed.CreateDecryptor();
> byte[] bytes = null;
> using (MemoryStream stream = new MemoryStream())
> {
> using (CryptoStream stream2 = new CryptoStream(stream,
> transform, CryptoStreamMode.Write))
> {
> stream2.Write(buffer, 0, buffer.Length);
> }
> bytes = stream.ToArray();
> }
> return Encoding.ASCII.GetString(bytes);
> }
> catch (Exception exception)
> {
> Console.Write (exception.ToString ());
> return string.Empty;
> }
> }
>
> And I have write a golang code as following:
>
> *func* test1(data, key string) {
> raw, err := base64.StdEncoding.DecodeString(data)
> *if* err != nil {
> *println*(err.Error())
> *return*
> }
>
> block, err := aes.NewCipher([]byte(key))
> *if* err != nil {
> *println*(err.Error())
> *return*
> }
> mode := cipher.NewCBCDecrypter(block, []byte(key)[:aes.BlockSize])
> mode.CryptBlocks(raw, raw)
>
> *println*(string(raw))
> }
>
> Besides the PKCS7 padding problem, I can’t get the right answer. Can
> someone help me with this? Where do I get this IV parameter?
> I Can’t set IV as C# does, because golang just complains about block size
> problem.
>
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