/*
 * 
 * SecureMemory, CryptoMemory and CryptoRF library
 *
 * Copyright (C) 2010, Flavio D. Garcia, Peter van Rossum, Roel Verdult
 * and Ronny Wichers Schreur. Radboud University Nijmegen   
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */

#include "cryptolib.h"

typedef enum {
  CA_ENCRYPT = 0x01,
  CA_DECRYPT = 0x02
} CryptoAction;

int counter=0;

byte_t nibbles_to_byte(nibble b0, nibble b1)
{
  // Combine both nibbles
  return ((b0<<4)|b1);
}

byte_t funny_mod(byte_t a, byte_t m)
{
  // Just return the input when this is less or equal than the modular value
  if (a<m) return a;
  
  // Compute the modular value
  a %= m;

  // Return the funny value, when the output was now zero, return the modular value
  return (a == 0) ? m : a;
}

byte_t bit_rotate_left(byte_t a, byte_t n_bits)
{
  // Rotate value a with the length of n_bits only 1 time
  byte_t mask = (1 << n_bits) - 1;
  return ((a << 1) | (a >> (n_bits - 1))) & mask;
}

void reconstruct_nibbles(crypto_state s)
{
  byte_t b1,b5,b8,b15,b18;
  byte_t b0,b4,b7,b14,b17;

  // Extract the bytes that generated the "previous" nibble
  b1 = (byte_t)((s->l >> 25) & 0x1f);
  b5 = (byte_t)((s->l >> 5) & 0x1f);
  b8 = (byte_t)((s->m >> 35) & 0x1f);
  b15 = (byte_t)((s->r >> 15) & 0x1f);
  b18 = (byte_t)(s->r & 0x1f);
  
  // Reconstruct the b0 nibble
  s->b0 = ((b1 ^ b5) & 0x0f) & ~(b8);
  s->b0 |= ((b15 ^ b18) & 0x0f) & b8;

  // Extract the bytes for the current nibble
  b0 = (byte_t)((s->l >> 30) & 0x1f);
  b4 = (byte_t)((s->l >> 10) & 0x1f);
  b7 = (byte_t)((s->m >> 42) & 0x1f);
  b14 = (byte_t)((s->r >> 20) & 0x1f);
  b17 = (byte_t)((s->r >> 5) & 0x1f);
  
  // Construct the values for b1 generation
  s->b1l = ((b0 ^ b4) & 0x0f);
  s->b1r = ((b14 ^ b17) & 0x0f);
  s->b1s = b7;

  // Reconstruct the b1 nibble
  s->b1 = s->b1l  & ~(s->b1s);
  s->b1 |= s->b1r &  s->b1s;
}

void next_left(byte_t in, crypto_state s)
{
  byte_t b3, b6, bx;
  
  // Update the left cipher state with the input byte
  s->l ^= ((in & 0x1f) << 20);

  // Extract the two (5 bits) values used for modular addtion
  b3 = (byte_t)((s->l >> 15) & 0x1f);
  b6 = (byte_t)(s->l & 0x1f);
  
  // Compute the modular addition
  bx = funny_mod(b3 + bit_rotate_left(b6,5),0x1f);

  // Rotate the left cipher state 5 bits
  s->l = ((s->l >> 5)| ((uint64_t)bx << 30));
  
  // Save the 4 left output bits used for b1
  s->b1l = ((bx^b3) & 0x0f);
}

void next_right(byte_t in, crypto_state s)
{
  byte_t b16, b18, bx;

  // Update the right cipher state with the input byte
  s->r ^= ((in & 0xf8) << 12);

  // Extract the two (5 bits) values used for modular addtion
  b16 = (byte_t)((s->r >> 10) & 0x1f);
  b18 = (byte_t)(s->r & 0x1f);

  // Compute the modular addition
  bx = funny_mod(b18 + b16,0x1f);

  // Rotate the right cipher state 5 bits
  s->r = ((s->r >> 5) | ((uint64_t)bx << 20));

  // Save the 4 right output bits used for b1
  s->b1r = ((bx^b16) & 0x0f);
}

void next_middle(byte_t in, crypto_state s)
{
  byte_t b12, b13, bx;
  
  // Update the middle cipher state with the input byte
  s->m ^= (((((uint64_t)in << 3) & 0x7f) | (in >> 5)) << 14);

  // Extract the two (7 bits) values used for modular addtion
  b12 = (byte_t)((s->m >> 7) & 0x7f);
  b13 = (byte_t)(s->m & 0x7f);

  // Compute the modular addition
  bx = (funny_mod(b12 + bit_rotate_left(b13,7),0x7f));

  // Rotate the middle cipher state 7 bits
  s->m = ((s->m >> 7)| ((uint64_t)bx << 42));

  // Save the 4 middle selector bits used for b1
  s->b1s = bx & 0x0f;
}

void next(const bool feedback, byte_t in, crypto_state s)
{
  // Initialize the (optional) input parameter
  byte_t a = in;

  // Only Cryptomemory uses feedback
  if (feedback)
  {
    // Construct the cipher update 'a' from (input ^ feedback)
    a = in ^ nibbles_to_byte(s->b0,s->b1);
  }

  // Shift the cipher state
  next_left(a,s);
  next_middle(a,s);
  next_right(a,s);

  // For active states we can use the available (previous) 'b1' nibble,
  // otherwise use reconstruct_nibbles() to generate them
  // reconstruct_nibbles(s)

  // The nible from b1 shifts to b0
  s->b0 = s->b1;

  // Construct the new value of nible b1
  s->b1 = s->b1l  & ~(s->b1s);
  s->b1 |= s->b1r &  s->b1s;
}

void next_n(const bool feedback, size_t n, byte_t in, crypto_state s)
{
  // While n-rounds left, shift the cipher
  while (n--) next(feedback,in, s);
}

void initialize(const bool feedback, const byte_t* Gc, const byte_t* Ci, const byte_t* Q, const size_t n, crypto_state s)
{
  size_t pos;

  // Reset the cipher state
  memset(s,0x00,sizeof(crypto_state_t));

  // Load in the ci (tag-nonce), together with the first half of Q (reader-nonce)
  for (pos = 0; pos < 4; pos++)
  {
    next_n(feedback,n,Ci[2*pos  ],s);
    next_n(feedback,n,Ci[2*pos+1],s);
    next(feedback,Q[pos],s);
  }

  // Load in the diversified key (Gc), together with the second half of Q (reader-nonce)
  for (pos = 0; pos < 4; pos++)
  {
    next_n(feedback,n,Gc[2*pos  ],s);
    next_n(feedback,n,Gc[2*pos+1],s);
    next(feedback,Q[pos+4],s);
  }
}

byte_t cm_byte(crypto_state s)
{
  // Construct keystream byte by combining both nibbles
  return nibbles_to_byte(s->b0,s->b1);
}

byte_t sm_byte(crypto_state s) {
  byte_t ks;

  // Construct keystream byte by combining 2 parts from 4 nibbles
  next_n(false,2,0,s);
  ks = s->b1 << 4;
  next_n(false,2,0,s);
  ks |= s->b1;

  return ks;
}

void print_crypto_state(const char* text,crypto_state s) {
    int pos;

    printf("%s",text);
    for(pos = 6; pos >= 0; pos--)
        printf(" %02x", (byte_t)(s->l >> (pos * 5)) & 0x1f);
    
    printf(" |");
    for(pos = 6; pos >= 0; pos--)
        printf(" %02x", (byte_t)(s->m >> (pos * 7)) & 0x7f);
    
    printf(" |");
    for(pos = 4; pos >= 0; pos--)
        printf(" %02x", (byte_t)(s->r >> (pos * 5)) & 0x1f);

    printf(" | %02x",cm_byte(s));
    printf("\n");
}

void sm_auth(const byte_t* Gc, const byte_t* Ci, const byte_t* Q, byte_t* Ch, byte_t* Ci_1, crypto_state s) {
    size_t pos;

    initialize(false,Gc,Ci,Q,1,s);

    // Generate challange answer for Tag and Reader
    for (pos=0; pos<8; pos++) {
        Ci_1[pos] = sm_byte(s);
        Ch[pos] = sm_byte(s);
    }
}

void cm_auth(const byte_t* Gc, const byte_t* Ci, const byte_t* Q, byte_t* Ch, byte_t* Ci_1, byte_t* Ci_2, crypto_state s) {
  size_t pos;

  initialize(true,Gc,Ci,Q,3,s);

  // Construct the reader-answer (challange)
  next_n(true,6,0,s);
  Ch[0] = cm_byte(s);
  for (pos = 1; pos < 8; pos++)
  {
    next_n(true,7,0,s);
    Ch [pos] = cm_byte(s);
  }
  
  // Construct the tag-answer (Ci+1 = ff .. .. .. .. .. .. ..)
  Ci_1[0] = 0xff;
  for (pos = 1; pos < 8; pos++)
  {
    next_n(true,2,0,s);
    Ci_1[pos] = cm_byte(s);
  }
  
  // Construct the session key (Ci+2)
  for (pos = 0; pos < 8; pos++)
  {
    next_n(true,2,0,s);
    Ci_2[pos] = cm_byte(s);
  }

  // Prepare the cipher for encryption by shifting 3 more times
  next_n(true,3,0,s);
}

void cm_crypt(const CryptoAction ca, const byte_t offset, const byte_t len, const byte_t* in, byte_t* out, crypto_state s) {
  size_t pos;
  byte_t bt;

  next_n(true,5,0,s);
  next(true,offset,s);
  next_n(true,5,0,s);
  next(true,len,s);
  for (pos=0; pos<len; pos++)
  {
    // Perform the crypto operation
    bt = in[pos] ^ cm_byte(s);
    
    // Generate output
    if (out) out[pos] = bt;

    // Detect where to find the plaintext for loading into cipher state
    if (ca == CA_DECRYPT)
    {
      next(true,bt,s);
    } else {
      next(true,in[pos],s);
    }
    
    // Shift the cipher state 5 times
    next_n(true,5,0,s);
  }
}

void cm_encrypt(const byte_t offset, const byte_t len, const byte_t* ct, byte_t* pt, crypto_state s) {
    next_n(true, 5, 0, s);
    next(true, 0, s);
    cm_crypt(CA_ENCRYPT, offset, len, ct, pt, s);
}

void cm_decrypt(const byte_t offset, const byte_t len, const byte_t* ct, byte_t* pt, crypto_state s) {
    next_n(true, 5, 0, s);
    next(true, 0, s);
    cm_crypt(CA_DECRYPT, offset, len, ct, pt, s);
}

void cm_grind_read_system_zone(const byte_t offset, const byte_t len, const byte_t* pt, crypto_state s) {
  cm_crypt(CA_ENCRYPT, offset, len, pt, null, s);
}

void cm_grind_set_user_zone(const byte_t zone, crypto_state s) {
    next(true, zone, s);
}

void cm_mac(byte_t* mac, crypto_state s) {
    next_n(true,10,0,s);
    if (mac) 
        mac[0] = cm_byte(s);

    next_n(true,5,0,s);
    if (mac)
        mac[1] = cm_byte(s);
}

void cm_password(const byte_t* pt, byte_t* ct, crypto_state s) {
    for (size_t pos = 0; pos < 3; pos++) {
        next_n(true, 5, pt[pos], s);
        ct[pos] = cm_byte(s);
    }
}