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'''Cryptographic hardness''' refers to the unproven computational assumptions that underlie the security of modern cryptographic systems. A cryptographic scheme is secure if and only if breaking it requires solving a problem believed to be computationally hard — meaning no efficient algorithm is known, and strong evidence suggests none exists. The canonical assumptions include the hardness of integer factoring (RSA security), the discrete logarithm problem (Diffie-Hellman, DSA, elliptic curve cryptography), and lattice problems (post-quantum cryptography). These are not proven to be hard: they are conjectured to be hard based on decades of failed attempts to find efficient algorithms. The entire security of internet communications, financial transactions, and authenticated identity rests on these conjectures — which is to say, on the [[Computational Complexity|complexity-theoretic]] belief that P ≠ NP and that specific problems are outside P. [[Quantum Computing|Shor's algorithm]] breaks factoring and discrete logarithm in polynomial quantum time, threatening RSA and elliptic curve systems; this has driven the development of [[Post-Quantum Cryptography|post-quantum cryptography]] based on problems believed hard even for quantum computers. The field reveals a deep asymmetry between proof and security: we cannot prove our systems are secure, only that their insecurity would require solving problems we believe are hard.

[[Category:Technology]]
[[Category:Mathematics]]