The Importance of "Good" Key Scheduling Schemes (How to Make a Secure DES Scheme with <= 48 Bit Keys)

In DES the key scheduling scheme uses mainly shift registers. By modifying this key scheduling, conventional cryptosystems can be designed which are, e.g., strong against exhaustive key search attacks (without increasing the key size), or have public key like properties. Other effects obtainable by modifying the key scheduling and their importance are discussed.