Let's suppose we have the plaintext, 14/16 char of the key and the first 2 and the last 36 chars of encrypted data (that is 64 char long). What I want is to find the IV. The cipher algorithm is AES (I think 128).
As I said, both the Key and the IV are 16 char long, the plaintext is exactly 32 char long and the cyphertext produced is 64.
What tool / process can I use to find the IV knowing all of this stuff? Note that I don't know the full key, but I have a big part of it, so probably some bruteforce is needed.
a = f(b, x)situation where you have everything you need to solve for
x, but you need to understand a bit better how
char=byte. if the message is 32 byte => you need padding and for CBC the most common is the PKCS#7 padding. The value is 16
0x10in hex. By using this and the last two ciphertexts one can find the key by looking the small 16-bit key search in known plaintetext attack. There are 4 bocks since usullay the IV is prepended to the ciphertext. It is not clear about the knowledge of the plaintext. If it is not known, one cannot find the IV, if known, it is a simple implementation... $\endgroup$