I use OpenSSL with
aes-256-cbc to encrypt a 30 GB tar file containing a recent backup of my hard drive. Now suppose somebody wants to run a brute-force attack on this file, trying out all possible password combinations. Does OpenSSL have to scan through the entire 30 GB of data in order to say whether the password matches or whether it doesn't match or can OpenSSL determine really quickly whether the specified password is the correct one?
In other words: Does it take longer to run a brute-force attack using OpenSSL on a 30 GB file than on a 100 KB file?