[Botan-devel] Botan IV key incompatibility?

[Jack Lloyd]

On Sun, Jul 01, 2007 at 03:16:40PM -0400, John Proffer wrote:
> Hi,
> 
> While trying to do database validation, and have encountered a problem - 
> seems that Botan's AES implementation is incompatible with that used by 
> PHP?  PHP needs an IV the same size as the blocksize (32 bytes).. 
> whereas Botan's IV only works on 16 bytes when using AES-256.

AES's blocksize is always 16 bytes (128 bits). Are you sure that PHP
is not requiring 32 bytes in hex (16 bytes of binary)?

> In the following code, Botan segfaults my application at cipher->set_iv(iv);
> 
>    Botan::byte mykey[33] =  {"Uf0zFs97zUNzPzHa9z_zz!z:L=ozxz!z"};
>    Botan::byte mypass[33] = {"UfzzFs97zUzzP2Ha98_az!z:L=ozxz!j"};
>    Botan::SymmetricKey key(mypass,32);
>    Botan::InitializationVector iv(mykey,32);
>    Keyed_Filter* cipher = get_cipher("AES-256/CFB/NoPadding", ENCRYPTION);
>    cipher->set_key(key);
>    cipher->set_iv(iv);
> 
> Shouldn't the IV be expecting 32 bytes when declaring AES-256 as the 
> cipher?  Am I calling this in the wrong order or something?
> 

It should not segfault. It does throw an exception:

$ ./a.out
terminate called after throwing an instance of 'Botan::Invalid_IV_Length'
  what():  Botan: IV length 32 is invalid for AES-256/CFB
Aborted

Jack