Cryptography
Cryptography (ancient Greek for “hidden,” “secret,” “write”) originally represented the science of encrypting information. Today, cryptography is primarily concerned with the subject of information security, i.e. the conception, definition and construction of information systems that prevent the unauthorized reading or alteration of information. Cryptography (the science of encrypting information), together with cryptanalysis (the science of analyzing encrypted information), forms cryptology (unites cryptography and cryptanalysis). Today’s cryptography includes four major goals for protecting information: Confidentiality/ access protection, integrity/ change protection, authenticity/ forgery protection, binding/ non-repudiation.
Methods of Cryptography:
Cryptographic methods are divided into classical and modern methods. This classification is based on the distinction between symmetric and asymmetric methods. As long as computers were not yet available for the encryption and decryption of data, whole letters or groups of letters were always substituted during encryption (e.g. “transposition”, “polyalphabetic substitution”). Today, in the age of electronic machines, this form of cryptography is considered obsolete and insecure. In accordance with the working method of modern computers, today’s cryptographic methods no longer work with complete letters, but with individual bits of the information data. This method increases the number of possible solutions many times over and also makes it possible to process data that is not text. These modern cryptographic applications can be divided into two subgroups: Symmetric methods, like classical cryptographic methods, use one secret key per communication relationship, as well as for all operations (e.g. encryption and decryption) of the method. Asymmetric methods use a secret or private key and a public key for each participant. Almost all asymmetric cryptographic methods are based on the use of mathematical structures such as lattices, rings or elliptic curves. They draw their security from the difficulties of explicit computational problems in these structures.
History of cryptography:
Cryptography has been used to encrypt information since the beginning of the third millennium BC. Starting with ancient Egyptian cryptography, newer and thus more complex methods of encryption have been created over the years. In the Middle Ages, for example, the most diverse forms of secret writing were used to protect correspondence between diplomats. The spread of the telegraph at the end of the 19th century led to the development of newer encryption techniques, which were expanded to include mechanical as well as electromechanical cryptography systems with the beginning of the Second World War. The age of modern and mathematically based cryptography began in the early fifties, when, after a period of secrecy of the cryptographic process, cryptography became more and more the focus of the public and the industrialized age.
