Using a compression function $f : A × A → A$. A basic version given by:
$W_0 = IV$
$W_1 = f(W_0, m_1)$
$W_2 = f(W_1, m_2)$
...
$W_n = f(W_{n-1}, m_n)$
$W_n$ is the output of the hash function, $m_1,m_2 . . . m_n$ is the message and $IV$ is a constant.
What would be the simplest way to implement AES-128 as the compression function? And would it be one way?
Excuse my ignorance, I am very new to the topic. My very wild stab in the dark is that AES-128 can be used in a way that feeds its own produced ciphertext blocks back into itself as the key.