mirror of
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403 lines
9.5 KiB
C++
403 lines
9.5 KiB
C++
/* Rijndael Block Cipher - aes.c
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Written by Mike Scott 21st April 1999
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mike@compapp.dcu.ie
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Permission for free direct or derivative use is granted subject
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to compliance with any conditions that the originators of the
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algorithm place on its exploitation.
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*/
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//#include <stdio.h>
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//#include <stdlib.h>
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#include <string.h>
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#define u8 unsigned char /* 8 bits */
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#define u32 unsigned long /* 32 bits */
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#define u64 unsigned long long
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/* rotates x one bit to the left */
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#define ROTL(x) (((x)>>7)|((x)<<1))
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/* Rotates 32-bit word left by 1, 2 or 3 byte */
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#define ROTL8(x) (((x)<<8)|((x)>>24))
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#define ROTL16(x) (((x)<<16)|((x)>>16))
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#define ROTL24(x) (((x)<<24)|((x)>>8))
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/* Fixed Data */
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static u8 InCo[4]={0xB,0xD,0x9,0xE}; /* Inverse Coefficients */
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static u8 fbsub[256];
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static u8 rbsub[256];
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static u8 ptab[256],ltab[256];
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static u32 ftable[256];
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static u32 rtable[256];
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static u32 rco[30];
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/* Parameter-dependent data */
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int Nk,Nb,Nr;
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u8 fi[24],ri[24];
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u32 fkey[120];
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u32 rkey[120];
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static u32 pack(u8 *b)
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{ /* pack bytes into a 32-bit Word */
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return ((u32)b[3]<<24)|((u32)b[2]<<16)|((u32)b[1]<<8)|(u32)b[0];
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}
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static void unpack(u32 a,u8 *b)
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{ /* unpack bytes from a word */
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b[0]=(u8)a;
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b[1]=(u8)(a>>8);
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b[2]=(u8)(a>>16);
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b[3]=(u8)(a>>24);
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}
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static u8 xtime(u8 a)
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{
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u8 b;
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if (a&0x80) b=0x1B;
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else b=0;
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a<<=1;
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a^=b;
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return a;
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}
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static u8 bmul(u8 x,u8 y)
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{ /* x.y= AntiLog(Log(x) + Log(y)) */
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if (x && y) return ptab[(ltab[x]+ltab[y])%255];
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else return 0;
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}
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static u32 SubByte(u32 a)
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{
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u8 b[4];
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unpack(a,b);
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b[0]=fbsub[b[0]];
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b[1]=fbsub[b[1]];
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b[2]=fbsub[b[2]];
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b[3]=fbsub[b[3]];
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return pack(b);
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}
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static u8 product(u32 x,u32 y)
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{ /* dot product of two 4-byte arrays */
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u8 xb[4],yb[4];
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unpack(x,xb);
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unpack(y,yb);
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return bmul(xb[0],yb[0])^bmul(xb[1],yb[1])^bmul(xb[2],yb[2])^bmul(xb[3],yb[3]);
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}
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static u32 InvMixCol(u32 x)
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{ /* matrix Multiplication */
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u32 y,m;
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u8 b[4];
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m=pack(InCo);
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b[3]=product(m,x);
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m=ROTL24(m);
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b[2]=product(m,x);
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m=ROTL24(m);
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b[1]=product(m,x);
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m=ROTL24(m);
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b[0]=product(m,x);
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y=pack(b);
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return y;
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}
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u8 ByteSub(u8 x)
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{
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u8 y=ptab[255-ltab[x]]; /* multiplicative inverse */
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x=y; x=ROTL(x);
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y^=x; x=ROTL(x);
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y^=x; x=ROTL(x);
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y^=x; x=ROTL(x);
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y^=x; y^=0x63;
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return y;
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}
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void gentables(void)
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{ /* generate tables */
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int i;
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u8 y,b[4];
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/* use 3 as primitive root to generate power and log tables */
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ltab[0]=0;
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ptab[0]=1; ltab[1]=0;
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ptab[1]=3; ltab[3]=1;
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for (i=2;i<256;i++)
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{
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ptab[i]=ptab[i-1]^xtime(ptab[i-1]);
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ltab[ptab[i]]=i;
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}
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/* affine transformation:- each bit is xored with itself shifted one bit */
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fbsub[0]=0x63;
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rbsub[0x63]=0;
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for (i=1;i<256;i++)
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{
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y=ByteSub((u8)i);
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fbsub[i]=y; rbsub[y]=i;
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}
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for (i=0,y=1;i<30;i++)
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{
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rco[i]=y;
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y=xtime(y);
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}
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/* calculate forward and reverse tables */
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for (i=0;i<256;i++)
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{
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y=fbsub[i];
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b[3]=y^xtime(y); b[2]=y;
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b[1]=y; b[0]=xtime(y);
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ftable[i]=pack(b);
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y=rbsub[i];
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b[3]=bmul(InCo[0],y); b[2]=bmul(InCo[1],y);
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b[1]=bmul(InCo[2],y); b[0]=bmul(InCo[3],y);
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rtable[i]=pack(b);
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}
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}
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void gkey(int nb,int nk,u8 *key)
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{ /* blocksize=32*nb bits. Key=32*nk bits */
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/* currently nb,bk = 4, 6 or 8 */
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/* key comes as 4*Nk bytes */
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/* Key Scheduler. Create expanded encryption key */
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int i,j,k,m,N;
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int C1,C2,C3;
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u32 CipherKey[8];
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Nb=nb; Nk=nk;
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/* Nr is number of rounds */
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if (Nb>=Nk) Nr=6+Nb;
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else Nr=6+Nk;
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C1=1;
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if (Nb<8) { C2=2; C3=3; }
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else { C2=3; C3=4; }
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/* pre-calculate forward and reverse increments */
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for (m=j=0;j<nb;j++,m+=3)
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{
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fi[m]=(j+C1)%nb;
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fi[m+1]=(j+C2)%nb;
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fi[m+2]=(j+C3)%nb;
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ri[m]=(nb+j-C1)%nb;
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ri[m+1]=(nb+j-C2)%nb;
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ri[m+2]=(nb+j-C3)%nb;
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}
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N=Nb*(Nr+1);
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for (i=j=0;i<Nk;i++,j+=4)
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{
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CipherKey[i]=pack(key+j);
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}
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for (i=0;i<Nk;i++) fkey[i]=CipherKey[i];
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for (j=Nk,k=0;j<N;j+=Nk,k++)
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{
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fkey[j]=fkey[j-Nk]^SubByte(ROTL24(fkey[j-1]))^rco[k];
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if (Nk<=6)
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{
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for (i=1;i<Nk && (i+j)<N;i++)
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fkey[i+j]=fkey[i+j-Nk]^fkey[i+j-1];
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}
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else
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{
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for (i=1;i<4 &&(i+j)<N;i++)
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fkey[i+j]=fkey[i+j-Nk]^fkey[i+j-1];
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if ((j+4)<N) fkey[j+4]=fkey[j+4-Nk]^SubByte(fkey[j+3]);
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for (i=5;i<Nk && (i+j)<N;i++)
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fkey[i+j]=fkey[i+j-Nk]^fkey[i+j-1];
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}
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}
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/* now for the expanded decrypt key in reverse order */
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for (j=0;j<Nb;j++) rkey[j+N-Nb]=fkey[j];
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for (i=Nb;i<N-Nb;i+=Nb)
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{
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k=N-Nb-i;
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for (j=0;j<Nb;j++) rkey[k+j]=InvMixCol(fkey[i+j]);
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}
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for (j=N-Nb;j<N;j++) rkey[j-N+Nb]=fkey[j];
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}
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/* There is an obvious time/space trade-off possible here. *
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* Instead of just one ftable[], I could have 4, the other *
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* 3 pre-rotated to save the ROTL8, ROTL16 and ROTL24 overhead */
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void encrypt(u8 *buff)
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{
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int i,j,k,m;
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u32 a[8],b[8],*x,*y,*t;
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for (i=j=0;i<Nb;i++,j+=4)
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{
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a[i]=pack(buff+j);
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a[i]^=fkey[i];
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}
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k=Nb;
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x=a; y=b;
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/* State alternates between a and b */
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for (i=1;i<Nr;i++)
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{ /* Nr is number of rounds. May be odd. */
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/* if Nb is fixed - unroll this next
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loop and hard-code in the values of fi[] */
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for (m=j=0;j<Nb;j++,m+=3)
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{ /* deal with each 32-bit element of the State */
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/* This is the time-critical bit */
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y[j]=fkey[k++]^ftable[(u8)x[j]]^
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ROTL8(ftable[(u8)(x[fi[m]]>>8)])^
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ROTL16(ftable[(u8)(x[fi[m+1]]>>16)])^
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ROTL24(ftable[(u8)(x[fi[m+2]]>>24)]);
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}
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t=x; x=y; y=t; /* swap pointers */
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}
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/* Last Round - unroll if possible */
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for (m=j=0;j<Nb;j++,m+=3)
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{
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y[j]=fkey[k++]^(u32)fbsub[(u8)x[j]]^
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ROTL8((u32)fbsub[(u8)(x[fi[m]]>>8)])^
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ROTL16((u32)fbsub[(u8)(x[fi[m+1]]>>16)])^
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ROTL24((u32)fbsub[(u8)(x[fi[m+2]]>>24)]);
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}
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for (i=j=0;i<Nb;i++,j+=4)
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{
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unpack(y[i],(u8 *)&buff[j]);
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x[i]=y[i]=0; /* clean up stack */
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}
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return;
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}
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void decrypt(u8 *buff)
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{
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int i,j,k,m;
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u32 a[8],b[8],*x,*y,*t;
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for (i=j=0;i<Nb;i++,j+=4)
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{
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a[i]=pack(buff+j);
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a[i]^=rkey[i];
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}
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k=Nb;
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x=a; y=b;
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/* State alternates between a and b */
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for (i=1;i<Nr;i++)
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{ /* Nr is number of rounds. May be odd. */
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/* if Nb is fixed - unroll this next
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loop and hard-code in the values of ri[] */
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for (m=j=0;j<Nb;j++,m+=3)
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{ /* This is the time-critical bit */
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y[j]=rkey[k++]^rtable[(u8)x[j]]^
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ROTL8(rtable[(u8)(x[ri[m]]>>8)])^
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ROTL16(rtable[(u8)(x[ri[m+1]]>>16)])^
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ROTL24(rtable[(u8)(x[ri[m+2]]>>24)]);
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}
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t=x; x=y; y=t; /* swap pointers */
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}
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/* Last Round - unroll if possible */
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for (m=j=0;j<Nb;j++,m+=3)
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{
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y[j]=rkey[k++]^(u32)rbsub[(u8)x[j]]^
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ROTL8((u32)rbsub[(u8)(x[ri[m]]>>8)])^
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ROTL16((u32)rbsub[(u8)(x[ri[m+1]]>>16)])^
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ROTL24((u32)rbsub[(u8)(x[ri[m+2]]>>24)]);
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}
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for (i=j=0;i<Nb;i++,j+=4)
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{
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unpack(y[i],(u8 *)&buff[j]);
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x[i]=y[i]=0; /* clean up stack */
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}
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return;
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}
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void aes_set_key( const u8 *key ) {
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gentables();
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gkey(4, 4, (u8*)key);
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}
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// CBC mode decryption
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void aes_decrypt(u8 *iv, const u8 *inbuf, u8 *outbuf, unsigned long long len) {
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u8 block[16];
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unsigned int blockno = 0, i;
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//fprintf( stderr,"aes_decrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len );
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//printf("aes_decrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len);
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for (blockno = 0; blockno <= (len / sizeof(block)); blockno++) {
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unsigned int fraction;
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if (blockno == (len / sizeof(block))) { // last block
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fraction = len % sizeof(block);
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if (fraction == 0) break;
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memset(block, 0, sizeof(block));
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} else fraction = 16;
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// debug_printf("block %d: fraction = %d\n", blockno, fraction);
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memcpy(block, inbuf + blockno * sizeof(block), fraction);
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decrypt(block);
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u8 *ctext_ptr;
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if (blockno == 0) ctext_ptr = iv;
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else ctext_ptr = (u8*)inbuf + (blockno-1) * sizeof(block);
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for(i=0; i < fraction; i++)
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outbuf[blockno * sizeof(block) + i] =
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ctext_ptr[i] ^ block[i];
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// debug_printf("Block %d output: ", blockno);
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// hexdump(outbuf + blockno*sizeof(block), 16);
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}
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}
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// CBC mode encryption
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void aes_encrypt(u8 *iv, const u8 *inbuf, u8 *outbuf, unsigned long long len) {
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u8 block[16];
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unsigned int blockno = 0, i;
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//printf("aes_decrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len);
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//fprintf( stderr,"aes_encrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len);
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for (blockno = 0; blockno <= (len / sizeof(block)); blockno++) {
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unsigned int fraction;
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if (blockno == (len / sizeof(block))) { // last block
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fraction = len % sizeof(block);
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if (fraction == 0) break;
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memset(block, 0, sizeof(block));
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} else fraction = 16;
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// debug_printf("block %d: fraction = %d\n", blockno, fraction);
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memcpy(block, inbuf + blockno * sizeof(block), fraction);
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for(i=0; i < fraction; i++)
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block[i] = inbuf[blockno * sizeof(block) + i] ^ iv[i];
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encrypt(block);
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memcpy(iv, block, sizeof(block));
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memcpy(outbuf + blockno * sizeof(block), block, sizeof(block));
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// debug_printf("Block %d output: ", blockno);
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// hexdump(outbuf + blockno*sizeof(block), 16);
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}
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}
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