# Is it possible to obtain AES-128 key from a known ciphertext-plaintext-iv tuple used the encrypt the plaintext? [duplicate]

i have a file, which was encrypted with AES-128 in CBC mode. I know the content of original file and know the iv used to encrypt that file.So, just wondering if it's possible to recover the key used from the information provided.

There are of course impractical attacks that work only in theory. You could just attempt $2^n$ distinct keys and you have a $1/2^n$ chance of finding the right one. But that means that you need $2^{127}$ attempts—about $1.7 \times 10^{38}$, an astronomically large number—to have a 50% chance of success.