void setrcon(byte rcon[10])
{
int i;
byte x=1;
for(i=0;i<10;i++)
{
rcon[i]=x;
x=multx(x);
}
}
// slow multiplication in GF(2^8)
byte mult(byte x,byte y)
{
int i;
byte z=0;
byte a=128;
for(i=7;i>=0;i--)
{
z=multx(z);
if((y & a)!=0) z^=x;
a=a >> 1;
}
return z;
}
void mixcolumns(byte *state)
{
byte ns[16];
int i,j;
for(j=0;j<4;j++)
{
ns[j*4]=multx(state[j*4]) ^ multx(state[j*4+1]) ^ state[j*4+1] ^ state[j*4+2] ^ state[j*4+3];
ns[j*4+1]=state[j*4] ^ multx(state[j*4+1]) ^ multx(state[j*4+2]) ^ state[j*4+2] ^ state[j*4+3];
ns[j*4+2]=state[j*4] ^ state[j*4+1] ^ multx(state[j*4+2]) ^ multx(state[j*4+3]) ^ state[j*4+3];
ns[j*4+3]=multx(state[j*4]) ^ state[j*4] ^ state[j*4+1] ^ state[j*4+2] ^ multx(state[j*4+3]) ;
}
for(j=0;j<4;j++)
for(i=0;i<4;i++)
state[j*4+i]=ns[j*4+i];
}
void mixcolumns_share(byte *stateshare[16],uint8_t n)
{
byte ns[16];
uint8_t i,j;
for(i=0;i<n;i++)
{
for(j=0;j<4;j++)
{
ns[j*4]=multx(stateshare[j*4][i]) ^ multx(stateshare[j*4+1][i]) ^ stateshare[j*4+1][i] ^ stateshare[j*4+2][i] ^ stateshare[j*4+3][i];
ns[j*4+1]=stateshare[j*4][i] ^ multx(stateshare[j*4+1][i]) ^ multx(stateshare[j*4+2][i]) ^ stateshare[j*4+2][i] ^ stateshare[j*4+3][i];
ns[j*4+2]=stateshare[j*4][i] ^ stateshare[j*4+1][i] ^ multx(stateshare[j*4+2][i]) ^ multx(stateshare[j*4+3][i]) ^ stateshare[j*4+3][i];
ns[j*4+3]=multx(stateshare[j*4][i]) ^ stateshare[j*4][i] ^ stateshare[j*4+1][i] ^ stateshare[j*4+2][i] ^ multx(stateshare[j*4+3][i]) ;
}
for(j=0;j<16;j++)
stateshare[j][i]=ns[j];
}
}