Cryptography or cryptology is the study and use of techniques for secure communication in the presence of unauthorized actors’ behavior. The practice uses various methods to prevent third parties or the public from reading private or unauthorized messages. This is done typically using encryption methods with modern cryptography being heavily based on mathematical theory and computer science practice.
Cryptographic algorithms are designed around computational hardness assumptions, making such algorithms hard to break in actual practice. Theoretically, it is possible to break into a hardened system but is not feasible to do so in actual practice.