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#include <iostream>
#include <iomanip>
#include <stdexcept>
#include <cstring>
#include <cassert>
#include "aes.h"
#include "gf28.h"
#include "rng.h"
using namespace std;
namespace AES{
//http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf (AES)
//https://tools.ietf.org/html/rfc3602 (CBC)
//State is represented in bytes, as is the key schedule (which is represented in words in the AES spec).
//State is in column-major order.
uint32_t roundconstant[10]={};
uint8_t sbox[256]={};
uint8_t invsbox[256]={};
void printstate(const uint8_t *state){
for(int i=0;i<16;i++){
cout<<setw(2)<<setfill('0')<<hex<<(int)state[i]<<dec;
}
cout<<endl;
}
void initTables(){
//generated tables have been checked with AES spec
int term=0x01;
for(int i=0;i<10;i++){
roundconstant[i]=term<<24;
term=GF28::multiply(term,0x02);
}
for(int i=0;i<256;i++){
uint8_t inv=(uint8_t)GF28(i).inverse();
uint8_t res=0;
for(int j=0;j<8;j++){
uint8_t bit=((inv>>j)&1)^
((inv>>((j+4)%8))&1)^
((inv>>((j+5)%8))&1)^
((inv>>((j+6)%8))&1)^
((inv>>((j+7)%8))&1);
res|=bit<<j;
}
res^=0x63;
sbox[i]=res;
invsbox[res]=i;
}
}
uint32_t subWord(uint32_t word){
return (sbox[word>>24]<<24)|(sbox[(word>>16)&0xff]<<16)|(sbox[(word>>8)&0xff]<<8)|sbox[word&0xff];
}
uint32_t rotWord(uint32_t word){
return (word<<8)|(word>>24);
}
void keyExpand(uint8_t *keysched,const uint8_t *key,int keylen,int numrounds){
memcpy(keysched,key,4*keylen);
for(int i=keylen;i<4*(numrounds+1);i++){
uint32_t temp=(keysched[4*i-4]<<24)|(keysched[4*i-3]<<16)|(keysched[4*i-2]<<8)|keysched[4*i-1];
if(i%keylen==0){
temp=subWord(rotWord(temp))^roundconstant[i/keylen-1];
} else if(keylen>6&&i%keylen==4){
temp=subWord(temp);
}
keysched[4*i+0]=keysched[4*(i-keylen)+0]^(temp>>24);
keysched[4*i+1]=keysched[4*(i-keylen)+1]^((temp>>16)&0xff);
keysched[4*i+2]=keysched[4*(i-keylen)+2]^((temp>>8)&0xff);
keysched[4*i+3]=keysched[4*(i-keylen)+3]^(temp&0xff);
}
}
void addRoundKey(uint8_t *state,const uint8_t *roundkey){
for(int i=0;i<16;i++)state[i]^=roundkey[i];
}
void subBytes(uint8_t *state){
for(int i=0;i<16;i++)state[i]=sbox[state[i]];
}
void shiftRows(uint8_t *state){
uint8_t t=state[1]; state[1]=state[5]; state[5]=state[9]; state[9]=state[13]; state[13]=t;
swap(state[2],state[10]); swap(state[6],state[14]);
t=state[3]; state[3]=state[15]; state[15]=state[11]; state[11]=state[7]; state[7]=t;
}
void mixColumns(uint8_t *state){
for(int i=0;i<4;i++){
uint8_t a=GF28::multiply(0x02,state[4*i+0]) ^ GF28::multiply(0x03,state[4*i+1]) ^ state[4*i+2] ^ state[4*i+3];
uint8_t b=state[4*i+0] ^ GF28::multiply(0x02,state[4*i+1]) ^ GF28::multiply(0x03,state[4*i+2]) ^ state[4*i+3];
uint8_t c=state[4*i+0] ^ state[4*i+1] ^ GF28::multiply(0x02,state[4*i+2]) ^ GF28::multiply(0x03,state[4*i+3]);
uint8_t d=GF28::multiply(0x03,state[4*i+0]) ^ state[4*i+1] ^ state[4*i+2] ^ GF28::multiply(0x02,state[4*i+3]);
state[4*i+0]=a;
state[4*i+1]=b;
state[4*i+2]=c;
state[4*i+3]=d;
}
}
void invShiftRows(uint8_t *state){
uint8_t t=state[1]; state[1]=state[13]; state[13]=state[9]; state[9]=state[5]; state[5]=t;
swap(state[2],state[10]); swap(state[6],state[14]);
t=state[3]; state[3]=state[7]; state[7]=state[11]; state[11]=state[15]; state[15]=t;
}
void invSubBytes(uint8_t *state){
for(int i=0;i<16;i++)state[i]=invsbox[state[i]];
}
void invMixColumns(uint8_t *state){
for(int i=0;i<4;i++){
uint8_t a=GF28::multiply(0x0e,state[4*i+0])^
GF28::multiply(0x0b,state[4*i+1])^
GF28::multiply(0x0d,state[4*i+2])^
GF28::multiply(0x09,state[4*i+3]);
uint8_t b=GF28::multiply(0x09,state[4*i+0])^
GF28::multiply(0x0e,state[4*i+1])^
GF28::multiply(0x0b,state[4*i+2])^
GF28::multiply(0x0d,state[4*i+3]);
uint8_t c=GF28::multiply(0x0d,state[4*i+0])^
GF28::multiply(0x09,state[4*i+1])^
GF28::multiply(0x0e,state[4*i+2])^
GF28::multiply(0x0b,state[4*i+3]);
uint8_t d=GF28::multiply(0x0b,state[4*i+0])^
GF28::multiply(0x0d,state[4*i+1])^
GF28::multiply(0x09,state[4*i+2])^
GF28::multiply(0x0e,state[4*i+3]);
state[4*i+0]=a;
state[4*i+1]=b;
state[4*i+2]=c;
state[4*i+3]=d;
}
}
void encryptBlock(uint8_t *state,const uint8_t *keysched,const uint8_t *data,int numrounds){
memcpy(state,data,16);
addRoundKey(state,keysched);
for(int round=0;round<numrounds-1;round++){
subBytes(state);
shiftRows(state);
mixColumns(state);
addRoundKey(state,keysched+16*(round+1));
}
subBytes(state);
shiftRows(state);
addRoundKey(state,keysched+16*numrounds);
}
void decryptBlock(uint8_t *state,const uint8_t *keysched,const uint8_t *data,int numrounds){
memcpy(state,data,16);
addRoundKey(state,keysched+16*numrounds);
for(int round=numrounds-2;round>=0;round--){
invShiftRows(state);
invSubBytes(state);
addRoundKey(state,keysched+16*(round+1));
invMixColumns(state);
}
invShiftRows(state);
invSubBytes(state);
addRoundKey(state,keysched);
}
string encryptCBC(const string &data,const string &key,int numrounds){
if(roundconstant[0]==0)initTables();
int sz=data.size();
if(sz==0)return {}; //if nothing to encrypt, don't even give an IV
int blocks=sz/16;
int padding=16-sz%16;
string res;
assert((sz+padding)%16==0);
res.reserve(16+sz+padding);
res.resize(16);
CryptoRng crng;
*(uint32_t*)&res[0]=crng.get(); //IV
*(uint32_t*)&res[4]=crng.get(); //endianness doesn't matter, since the data is random anyway
*(uint32_t*)&res[8]=crng.get();
*(uint32_t*)&res[12]=crng.get();
uint8_t keysched[16*(numrounds+1)];
keyExpand(keysched,(const uint8_t*)key.data(),key.size()/4,numrounds);
uint8_t buf[16],inbuf[16];
for(int i=0;i<blocks;i++){
memcpy(inbuf,data.data()+16*i,16);
for(int j=0;j<16;j++)inbuf[j]^=res[res.size()-16+j]; //the CBC xor step
encryptBlock(buf,keysched,inbuf,numrounds);
res.insert(res.size(),(char*)buf,16);
}
if(padding<16)memcpy(inbuf,data.data()+16*blocks,16-padding);
memset(inbuf+16-padding,padding,padding);
for(int j=0;j<16;j++)inbuf[j]^=res[res.size()-16+j]; //the CBC xor step
encryptBlock(buf,keysched,inbuf,numrounds);
res.insert(res.size(),(char*)buf,16);
return res;
}
string decryptCBC(const string &data,const string &key,int numrounds){
if(roundconstant[0]==0)initTables();
if(data.size()==0)return {};
if(data.size()%16!=0)throw invalid_argument("AES encrypted data not multiple of block size");
int blocks=data.size()/16-1; //the IV is not counted as a block
string res(16*blocks,'\0');
uint8_t keysched[16*(numrounds+1)];
keyExpand(keysched,(const uint8_t*)key.data(),key.size()/4,numrounds);
for(int i=blocks-1;i>=0;i--){
decryptBlock((uint8_t*)&res[16*i],keysched,(const uint8_t*)data.data()+(16+16*i),numrounds);
for(int j=0;j<16;j++)res[16*i+j]^=data[16*i+j]; //CBC: xor with the previous (remember the IV taking up space)
}
int padsize=res.back();
if(padsize>16||padsize<0)throw invalid_argument("Malformed AES padding");
res.resize(res.size()-padsize);
return res;
}
string encrypt(const string &data,const string &key,Algorithm algo){
int increment;
switch(algo){
case AES_128_CBC: increment=0; break;
case AES_192_CBC: increment=1; break;
case AES_256_CBC: increment=2; break;
default: assert(false);
}
assert((int)key.size()==4*(4+2*increment));
return encryptCBC(data,key,10+2*increment);
}
string decrypt(const string &data,const string &key,Algorithm algo){
int increment;
switch(algo){
case AES_128_CBC: increment=0; break;
case AES_192_CBC: increment=1; break;
case AES_256_CBC: increment=2; break;
default: assert(false);
}
assert((int)key.size()==4*(4+2*increment));
return decryptCBC(data,key,10+2*increment);
}
}
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