/* SBox8: 8 bit Pseudo-Random Number Generator Algorithm/Source Code */

/*
This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <http://unlicense.org/>

#** SBox8 algorithm originally designed and developed by Karl-Uwe Frank

*/
//**********************************************************************

// rm -f ./SBox8_for_tests; gcc -std=c99 -O3 -fomit-frame-pointer -mtune=native SBox8_for_tests.c -o SBox8_for_tests
//
// ./SBox8_for_tests seed key < in_Byte > SBox8_rng_out.bin
//
// ./SBox8_for_tests 0x2ddd6a2c 0c8c8279b04c4430d69a6454d069458e < ~/Public/zero_4kb.bin > SBox8_rng_out.bin
//
// ./SBox8_for_tests 0x00f75bce a619e43a58d095f5aaf2c5a235097a9e < ~/Public/zero_4kb.bin > SBox8_rng_out.bin
// 
// ./SBox8_for_tests 0xdeadbeef 04c7a580a0c8e7bf7ec5a0c9aef63c81 < ~/Public/zero_64kb.bin > SBox8_rng_out.bin



#include <stdlib.h>
#include <stdio.h> 
#include <string.h>
#include <time.h>
// needed to generate uint32 on a 64bit OS
#include <stdint.h>

///////////////////////////////////////////

#define swap(X,Y) { uint8_t T = X; X = Y; Y = T; }



int main (int argc, char *argv[]) { 
	uint8_t  a, b, c, d, j;
	uint8_t  SBox[256];
	uint32_t seed;

	// Check if a Seed and a Key is passed through
 	if (argc < 3) {
		fprintf(stderr, "\nUsage  : %s Seed (in Hex) Key(in Hex) <in >out\n", argv[0]);
		fprintf(stderr, "\nExample: %s 78e68cf3 7d0ef66789aca2cfa6c76db7560554 <Plainfile >CipherFile\n", argv[0]);
		fprintf(stderr, "\n         cat CipherFile | %s 78e68cf3 7d0ef66789aca2cfa6c76db7560554 > Plainfile\n\n", argv[0]);
 		return 1;
 	}	
		
 	seed = (int)strtoul(argv[1], NULL, 16); 	

	// We have a Keyword
	uint8_t keyword[256];
	uint8_t keyLen;
	uint8_t hexKey[256];
	uint8_t hex[3]; 

	// Make sure the arrays get initialised properly
	// and wipe out anything which might be there
	memset(keyword, 0, 256);
	memset(hexKey,  0, 256);
	memset(hex,     0, 3);

	// Rebuild KeyWord[] from KeyHash
	strcpy(hexKey, argv[2]);
	keyLen = strlen(hexKey);
	hexKey[keyLen] = 0;

	keyLen = keyLen/2;
	for (uint8_t i=0; i<keyLen; i++) {
		strncpy(hex, hexKey +(i*2), 2);
		keyword[i] = strtol(hex, NULL, 16);
	}

	if (seed == 0) {
		a = 14;
		b = 59;
		c = 23;
		d = 77;	
	} else {	
		a = ( seed        & 0xff);
		b = ((seed >>  8) & 0xff);
		c = ((seed >> 16) & 0xff);
		d = ((seed >> 24) & 0xff);
	}

	// Shifting in Order to generate an alternating Permutation
	while (( b % 8) != 3) b++;
	while (((c % 8) != 5) && ((c % 8) != 7)) c++;
	while (((d % 8) != 5) && ((d % 8) != 7)) d++;

	// Initialise the alternating Permutation
	memset(SBox,  0, sizeof(SBox));
	
	for (int i=0; i<256; i++) {
		a = (a + (b ^ c) + d);
		SBox[i] = a;
	}

	// Shuffle the Keyword into the Permutation
	for (int i=0; i<256; i++) {
		d  = i % keyLen;
		
		a += SBox[b];
		b += SBox[a];
		c  = a + b + i + keyword[d];
		
		swap(SBox[c], SBox[i]);		
	}

  // Encrypt/Decrypt Binary File(buffered Read/Write)
  int bufferRead;
  const    int  BUF_SIZE = 65536;
  unsigned char inB[BUF_SIZE], outB[BUF_SIZE];
	memset(inB,  0, sizeof(inB));
	memset(outB, 0, sizeof(outB));

  fflush(stdin);
  fflush(stdout);

	j=0;
	
  while ((bufferRead = fread(&inB, sizeof(char), BUF_SIZE, stdin)) > 0) {
		for (int i=0; i<bufferRead; i++) {
			a += SBox[b];
			b += SBox[a];
			c  = a + b + j + SBox[j];
			
			swap(SBox[c], SBox[j]);		
	
			d  = SBox[(SBox[c] + SBox[d]) &0xff];

			outB[i] = ((a + b) ^ (c + d));
    
	    j++;
		}

    // Redirect Output to stdout
    fwrite(&outB, sizeof(char), bufferRead, stdout);    

		// Reset the Byte Buffer to Zero
		memset(inB,  0, sizeof(inB));
		memset(outB, 0, sizeof(outB));
	}

  fflush(stdin);
  fflush(stdout);

	return 0;
}