In the past, cryptographers sometimes relied on security through obscurity, keeping both the method and the key secret. Modern best practice rejects this, because once an obscured method is discovered—often by reverse engineering—security collapses completely. By publishing algorithms and allowing open scrutiny, weaknesses can be identified and corrected before they are exploited at scale. Widely used algorithms like AES, RSA, and SHA have undergone years of public review, and their continued security depends primarily on the infeasibility of guessing or computing the correct keys within a practical timeframe.
A striking historical example of how computational power creep affects algorithm viability is the case of the Data Encryption Standard (DES). When DES was adopted in 1977, its 56-bit key was considered secure against all practical brute-force attacks, given the computing capabilities of the time. However, advances in hardware and parallel processing drastically reduced the cost and time needed to exhaust all possible keys. By the late 1990s, purpose-built machines could break a DES key in less than a day. This demonstrated that DES’s key length was no longer sufficient, even though the core algorithm itself remained mathematically sound.
Modern encryption standards like AES use key lengths of 128 bits or more, which are currently considered computationally infeasible to brute-force with existing or near-term technology. This shift illustrates a crucial lesson in cryptography: even strong algorithms must be paired with sufficiently large keys to remain secure over time. Transparency in algorithm design allows the security community to focus on monitoring and updating key length recommendations as computing power evolves.