Today's encryption algorithms can be broken. Their security derives from the wildly impractical lengths of time it can take to do so. Let's say you're using a 128-bit AES cipher. If a quantum system had to crack a 256-bit key, it would take about as much time as a conventional computer needs to crack a 128-bit key.
Keeping this in view, how secure is a 256 bit encryption?
The cipher AES-256 is used among other places in SSL/TLS across the Internet. It's considered among the top ciphers. In theory it's not crackable since the combinations of keys are massive. Although NSA has categorized this in Suite B, they have also recommended using higher than 128-bit keys for encryption.
How long does it take to break a 128 bit encryption?
As shown above, even with a supercomputer, it would take 1 billion billion years to crack the 128-bit AES key using brute force attack. This is more than the age of the universe (13.75 billion years).
How safe is 128 bit encryption?
128-bit encryption is a data/file encryption technique that uses a 128-bit key to encrypt and decrypt data or files. It is one of the most secure encryption methods used in most modern encryption algorithms and technologies. 128-bit encryption is considered to be logically unbreakable.