Consider the double $($ASCII$)$ Vigen$`$ere cipher, where we choose two keys $($possibly of different

lengths$)$ k$1,$ k$2,$ and then encrypt a message by encrypting it first using the ASCII Vigen$`$ere

cipher with k$1$ to obtain an intermediate ciphertext c

$$

$,$ and then encrypting c

$$ using the ASCII

Vigen$`$ere cipher with k$2$ to obtain the final ciphertext c$.$ How would you attack this scheme?