Block ciphers are cryptographic algorithms that encrypt data in fixed-size blocks. They are used to secure data in transit, such as in internet communications, and to store data securely, such as in databases. Block ciphers use a symmetric key, meaning that the same key is used to both encrypt and decrypt the data. Block ciphers are typically faster and more efficient than stream ciphers, and are used in a variety of applications, including secure web browsing, file encryption, and secure communications.
