Encryption

Encryption scrambles information so that only somebody with the right key can turn it back into something readable.

The maths is the part people worry about and almost never the part that fails. What decides whether encryption actually protects anything is how the key is looked after. A locked box is only as good as where you keep the key, and the same is true here. If the key sits next to the data, or everybody has a copy, or it can be reset by anyone who can answer a security question, the strength of the scrambling stops being the point. Nearly every real failure is a key handling failure.