Specified key is not a valid size for this algorithm...

Question

Hi,

I have with this code:

RijndaelManaged rijndaelCipher = new RijndaelManaged();

            // Set key and IV
            rijndaelCipher.Key = Convert.FromBase64String("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz012345678912");
            rijndaelCipher.IV = Convert.FromBase64String("1234567890123456789012345678901234567890123456789012345678901234");

I get throws :

Specified key is not a valid size for this algorithm.

Specified initialization vector (IV) does not match the block size for this algorithm.

What's wrong with this strings ? Can I count at some examples strings from You ?

Answer 1

The RijndaelManaged algorithm supports key lengths of 128, 192, or 256 bits. Is your key one of these sizes?

Answer 2

The string "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz012345678912" when base64-decoded yields 48 bytes (384 bits). RijndaelManaged supports 128, 192 and 256 bit keys.

A valid 128-bit key is new byte[]{ 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F } or if you need to get it from base64 : Convert.FromBase64String("AAECAwQFBgcICQoLDA0ODw==").

The default blocksize is 128 bits, so the same byte-array will work as the IV.