CryptologyIt is the study of cryptography and cryptanalysis.CryptographyViewed in social terms, it is the science of making the cost of acquiring or altering information improperly greater than the possible value obtained by doing so.Viewed in more formal terms, it is the practice and study of techniques of encryption and decryption of information, that is, techniques to encode a message making it unintelligible (encryption) and retrieve the original message from that unintelligible (decrypted) version.Cryptographic algorithmIt is a mathematical method used to encrypt and decrypt a message. It generally works by using one or more keys (numbers or strings of characters) as parameters of the algorithm, so that they are necessary to retrieve the message from the encrypted version.The message before encrypting is called clear text and once encrypted it is called encrypted text.Cryptographic systemIt is a system to encrypt and decrypt information composed of a set of cryptographic algorithms, keys and, possibly, several clear texts with their corresponding versions in encrypted text.Current cryptographic systems are based on three types of cryptographic algorithms: secret or symmetric key, public key or asymmetric and message summary (dispersion functions).Message summary algorithmsTransform variable size messages to fixed-size encrypted texts without using keys. They are used to convert large messages into more manageable representations.Secret or symmetric key algorithmsThey convert a message into an encrypted text of the same size as the original. They use a single key to encrypt and decrypt. They are the algorithms used to transfer large amounts of information safely.Public key or asymmetric algorithmsThey encrypt a message generating an encrypted text of the same size as the original. They use one key to encrypt the message (private key) and another to decrypt (public key). They have a high computational cost and are usually used to distribute the keys of the symmetric algorithms.CryptanalysisIt is the set of procedures, processes and methods used to break a cryptographic algorithm, decipher an encrypted text or discover the keys used to generate it.