When data is exchanged among parties, it can be intersected and modified by a malicious party. For this reason, data needs to be authenticated. To accomplish that, a token of information accompanies each packet of data. This token is called a hash. Hashing is not the same as ciphering. When data is ciphered, it can be deciphered. However, a hash does not return the information from which it derives. What the hash proves is that the data is authentic. For example, party A sends a file to party B and a hash is calculated on the data. A determined algorithm processes the data together with a secret keyword. Both the data and the hash are sent to B. When party B receives the data, it proceeds to calculate the hash. If the resulting hash matches the one that accompanies the data, then it is assumed that the data has not been changed in transit. Hence, the hash acts as a checksum and it proves data authenticity