In cryptography, a cipher is a digital security algorithm that encrypts and decrypts data. A website or software’s security system feeds data, like text or code, to the cipher, which then carefully turns it into random, unreadable data, also called ciphertext. If anyone intercepts or tries to steal this data, it won’t be useful to them. But once the data reaches its destination, the cipher reverses the process and translates it back to its original state.
Different kinds of cipher algorithms vary in complexity. For example, some transpose data by mixing and scrambling it, while others substitute data with different letters or numbers. Some ciphers encrypt data in big blocks, and some constantly encrypt data in a stream as the cipher receives it. It all depends on the needs of the website or software.