Editing Key schedule (section)

{{Short description|Algorithm that calculates all the round keys from the key}}
{{Refimprove|date=July 2008}}

[[Image:DES-key-schedule.png|thumbnail|220px|The key schedule of DES ("<<<" denotes a left rotation), showing the calculation of each round key ("Subkey").]]

In [[cryptography]], the so-called [[product cipher]]s are a certain kind of cipher, where the (de-)ciphering of data is typically done as an iteration of ''[[Round (cryptography)|rounds]]''.  The setup for each round is generally the same, except for round-specific fixed values called a [[round constant]], and round-specific data derived from the [[key (cryptography)|cipher key]] called a '''round key'''.  A '''key schedule''' is an algorithm that calculates all the round keys from the key.