The two most important goals of cryptography are providing confidentiality, authenticity and integrity of messages that are sent through insecure communication channel. Confidentiality ensures that the message is readable only by the original recipient, while for the others it’s ineligible. Confidentiality is achieved by encryption schemes where the plaintext is converted into ciphertext and in this form it is sent through communication channel. Data integrity is a feature that ensures that data is not altered or forged by unauthorized parts of communication. Integrity is usually achieved by message authentication codes, MACs. MAC is an algorithm for generating a short data string which is added to the original message to ensure the authentication of the sender and the integrity of the sent message. Many applications use encryption algorithms and MAC together, each algorithm with its own key, to accomplish these goals. However, not every combination of secure encryption schemes and a secure message authentication code can provide required properties. It can be shown that only the method encrypt-then-authenticate, where the message is first encrypted and then a MAC tag is computed over the encrypted message, provides both properties. More recently, the idea of providing confidentiality and data integrity is emerging using only one single-key algorithm. The problem of using two algorithms is solved with the phenomenon of authenticated encryption, which instead of two separate algorithms uses one single-key algorithm that combines functions that provide both confidentiality and integrity of the message.