Every current encryption scheme is based upon an *algorithm*, a step-by-step, recursive computational procedure for solving a problem in a finite number of steps. The cryptographic algorithm—what is commonly called the *encryption algorithm* or *cipher*—is made up of mathematical steps for encrypting and decrypting information. Figure 4-1 shows a diagram of the encryption and decryption process and its parts. There are three types of encryption algorithms commonly used, the *symmetric*, *asymmetric*, and *hashing* algorithms. Symmetric algorithms are also known as *shared secret* algorithms, as the same key is used for encryption and decryption. Asymmetric algorithms use a very different process using two keys, a public key and a private key, making ...

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