f function Combine 32 bit input and 48 bit key into 32 bit output Expand 32 bit input to 48 bits XoR the 48 bit key with the expanded 48 bit input Apply the s-boxes to the 48 bit input to produce 32 bit output Permute the resulting 32 bits 1717 f function Combine 32 bit input and 48 bit key into 32 bit output • Expand 32 bit input to 48 bits • XOR the 48 bit key with the expanded 48 bit input • Apply the S-boxes to the 48 bit input to produce 32 bit output • Permute the resulting 32 bits