The invention includes a security key generator in use for receiving first, second and third input cipher keys. The generator generates a first output cipher key by using the first, second and third input cipher keys. The first, second and third input cipher keys are as user cipher key, cipher key selection and cipher key variable respectively. The first output cipher key, which is different from the first input key, can be unique, and it is not a weak key or semiweak key. The first, second and third input cipher keys could be mapped to generate mapped data of cipher key. Middle cipher key is generated based on first input cipher key. The middle cipher key and output data of cipher key can be scrambled in order to generate a scrambled output. At least part of the output data of cipher key can be shielded. XOR process is carried out between the shielded part and the scrambled output to generate first output cipher key.