In the source code there's a comment on line 45 telling you to change the cipher only.
Code:
u8 cipher[32]={
//change only this :
0x1c,0x20,0xc1,0xa7,0x3b,0x25,0xaf,0x18,0xc8,0x6e,0x1b,0x41,0xfe,0x69,0xd6,0xc6,
0xde,0x3b,0x00,0xf8,0x17,0x48,0xde,0x04,0x9e,0xb5,0xaf,0xf2,0x70,0x8c,0xd9,0xda,
//
};
