Cryptography

Cryptography, often known as cryptology, is the art of and the study of various methods for safe communication in the midst of hostile activity. In a broader sense, the field of cryptography focuses on the construction and analysis of protocols that prohibit unauthorised individuals or the general public from accessing private communications. Mathematics, computer science, information security, electrical engineering, digital signal processing, physics, and a number of other fields all converge at the crossroads where modern cryptography is created. Cryptography is built on some of the most fundamental ideas underlying information security, including non-repudiation, authentication, data integrity, and secrecy of stored information. Cryptography has many real-world uses, including as electronic commerce, chip-based payment cards, digital currencies, computer passwords, and secure military communications.

Before the advent of the modern era, cryptography was almost identical with encryption. This technique included transforming information that could be read, known as plaintext, into incomprehensible nonsensical text, known as ciphertext (decryption). To prevent unauthorised access from third parties, the sender of a communication that has been encrypted (or coded) will only provide the method required to decode the message to the individuals who are supposed to receive it. In the literature on cryptography, the names "Alice" (or "A"), "Bob" (or "B"), and "Eve" (or "E") are often used to refer to the sender, the intended receiver, and the eavesdropping opponent, respectively. Since the invention of rotor cypher machines during World War I and the arrival of computers during World War II, cryptographic techniques have gotten more complicated, and the range of applications for these methods has expanded significantly.

Cryptography nowadays is strongly dependent on mathematical theory and the practical application of computer science; cryptographic methods are constructed with computational hardness assumptions in mind, which makes it difficult for any adversary to crack such algorithms in real practise. Although it is conceivable to break into a well-designed system in theory, it is not practical to do so in real practise. Schemes that are information-theoretically secure and that can demonstrably not be broken even with an unlimited amount of computing power, such as the one-time pad, are significantly more challenging to use in practise than the best schemes that are theoretically breakable but computationally secure.

The proliferation of cryptographic technology in the Information Age has given rise to a variety of legal questions. Due to the fact that cryptography has the potential to be used as a tool for espionage and sedition, several countries have designated it as a weapon and placed restrictions on its usage as well as export bans or even outright banned it. The revelation of encryption keys for documents that are pertinent to an inquiry may be compelled by law in certain countries. These jurisdictions are those in which the use of cryptography is permitted. In the context of digital media, cryptography is also essential for digital rights management and the resolution of disputes involving the violation of intellectual rights.