Encryption algorithms are complex mathematical equations that use a number, called a key, to change the data before transmission. In order to decrypt the transmission, the decoder must use the same key that was used to encrypt it. The decoder reverses the calculations of the encoder and, if the key is the same, the original data is recovered. Encrypting the transmission prevents an outsider from being able to view or alter the data. However, the complicated calculations require significant processor overhead. As some encryption algorithms become standardized many radios are including dedicated encryption engines to reduce the processor requirements and lower the power consumption and cost. One of the most popular encryption algorithms for low power devices is AES; Skipjack, PGP and DES are some other examples, though there are many other algorithms.