Modern cryptography builds on centuries of human ingenuity, but its defining feature is the reliance on publicly available, mathematically robust algorithms combined with secure key management. The shift from secrecy of method to openness of design aligns directly with Kerckhoffs’s principle—an algorithm’s strength must come from its resistance to cryptanalysis, not from keeping it hidden. This transparency allows cryptographic algorithms to be reviewed, tested, and improved by the global security community, which is essential for long-term trust.