Cryptography

Cryptography is the discipline that designs and analyses algorithms for protecting data and communications against eavesdropping, tampering, and impersonation. Modern cryptography combines number theory, algebra, probability, and complexity theory to build primitives such as block and stream ciphers, public-key systems, hash functions, message authentication codes, and digital signatures. Cryptographic security is generally evaluated under formal models (e.g., IND-CPA, EUF-CMA) and relies on hard mathematical problems like integer factorization, discrete logarithms, or learning-with-errors. Standards bodies such as NIST, ISO, and IETF publish vetted algorithms; ad-hoc or homegrown crypto is strongly discouraged because subtle flaws are catastrophic and rarely visible without expert review.