Uncrackability

So that although the Director may have been the anguished figure earlier described, distressed at having to sacrifice a handful of agents in order to save his country, it is equally possible that he was a stolid bureaucrat pinning his simple faith on the uncrackability of his codes.

Source: wiktionary

The makers argue that foreign encryption software will rush in to fill the gap, doing nothing about the uncrackability problem – indeed, making it worse.

Source: wiktionary

The uncrackability of one-time pads requires they must be completely random and never seen or used before or after.

Source: wiktionary