path: root/idea.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
#include <limits.h>
#include <time.h>

#include "cleanbench.h"
#include "randnum.h"


/********************
** IDEA Encryption **
*********************
** IDEA - International Data Encryption Algorithm.
** Based on code presented in Applied Cryptography by Bruce Schneier.
** Which was based on code developed by Xuejia Lai and James L. Massey.
** Other modifications made by Colin Plumb.
**
*/

/* Following constant defines the max number of loops the
** system will attempt. Keeps things from going off into the
** weeds. */
/*#define LOOP_MAX 50000L*/
#define LOOP_MAX 500000L

/*
** Following constant sets the size of the arrays.
** NOTE: For the IDEA algorithm to work properly, this
**  number MUST be some multiple of 8.
*/
#define ARRAY_SIZE 4000

#define IDEAKEYSIZE 16
#define IDEABLOCKSIZE 8
#define ROUNDS 8
#define KEYLEN (6*ROUNDS+4)

#define low16(x) ((x) & 0x0FFFF)
#define MUL(x,y) (x=mul(low16(x),y))

typedef uint16_t IDEAkey[KEYLEN];

static clock_t DoIDEAIteration(unsigned char *plain1,
	unsigned char *crypt1, unsigned char *plain2,
        unsigned long nloops, IDEAkey Z, IDEAkey DK);
static uint16_t mul(register uint16_t a, register uint16_t b);
static uint16_t inv(uint16_t x);
static void en_key_idea(uint16_t userkey[8], IDEAkey Z);
static void de_key_idea(IDEAkey Z, IDEAkey DK);
static void cipher_idea(uint16_t in[4], uint16_t out[4], IDEAkey Z);

/***********
** DoIDEA **
************
** Perform IDEA encryption.  Note that we time encryption & decryption
** time as being a single loop.
*/
double
DoIDEA(void)
{
        unsigned char*  plain1 = NULL;               /* First plaintext buffer */
        unsigned char*  crypt1 = NULL;               /* Encryption buffer */
        unsigned char*  plain2 = NULL;               /* Second plaintext buffer */
        clock_t         total_time = 0;
        int             iterations = 0;
        IDEAkey         Z, DK;
        uint16_t        userkey[8];
        int             i;
        static bool     is_adjusted = false;
        static int      loops = 100;

        randnum(3);

        /*
        ** Build an encryption/decryption key
        */
        for ( i = 0; i < 8; i++) {
                userkey[i] = (uint16_t)(abs_randwc((int32_t)60000) & 0xFFFF);
        }
        for(i = 0; i < KEYLEN ; i++) {
                Z[i] = 0;
        }

        /*
        ** Compute encryption/decryption subkeys
        */
        en_key_idea(userkey,Z);
        de_key_idea(Z,DK);

        /*
        ** Allocate memory for buffers.  We'll make 3, called plain1,
        ** crypt1, and plain2.  It works like this:
        **   plain1 >>encrypt>> crypt1 >>decrypt>> plain2.
        ** So, plain1 and plain2 should match.
        ** Also, fill up plain1 with sample text.
        */
        plain1 = malloc(ARRAY_SIZE);

        crypt1 = malloc(ARRAY_SIZE);

        plain2 = malloc(ARRAY_SIZE);

        /*
        ** Note that we build the "plaintext" by simply loading
        ** the array up with random numbers.
        */
        for (i = 0;i < ARRAY_SIZE; i++) {
                plain1[i] = (unsigned char)(abs_randwc(255) & 0xFF);
        }

        /*
        ** See if we need to perform self adjustment loop.
        */
        if (is_adjusted == false) {
                is_adjusted = true;
                /*
                ** Do self-adjustment.  This involves initializing the
                ** # of loops and increasing the loop count until we
                ** get a number of loops that we can use.
                */
                do {
                        loops += 10;
                } while((DoIDEAIteration(plain1, crypt1, plain2, loops, Z, DK) <= MINIMUM_TICKS) && (loops < LOOP_MAX));
        }

        /*
        ** All's well if we get here.  Do the test.
        */

        do {
                total_time += DoIDEAIteration(plain1, crypt1, plain2, loops, Z, DK);
                iterations += loops;
        } while (total_time < MINIMUM_SECONDS * CLOCKS_PER_SEC);

        free(plain1);
        free(crypt1);
        free(plain2);

        return (double)(iterations * CLOCKS_PER_SEC) / (double)total_time;
}

/********************
** DoIDEAIteration **
*********************
** Execute a single iteration of the IDEA encryption algorithm.
** Actually, a single iteration is one encryption and one
** decryption.
*/
static clock_t
DoIDEAIteration(unsigned char *plain1, unsigned char *crypt1, unsigned char *plain2, unsigned long nloops, IDEAkey Z, IDEAkey DK)
{
	clock_t start, stop;
	register unsigned long i;
	register unsigned long j;

	start = clock();

	for (i = 0; i < nloops; i++) {
		for (j = 0; j < ARRAY_SIZE; j += sizeof(uint16_t) * 4) {
			cipher_idea((uint16_t *)(plain1 + j), (uint16_t *)(crypt1 + j), Z);       /* Encrypt */
		}

		for (j = 0; j < ARRAY_SIZE; j += sizeof(uint16_t) * 4) {
			cipher_idea((uint16_t *)(crypt1 + j), (uint16_t *)(plain2 + j), DK);      /* Decrypt */
		}
	}

	stop = clock();

	return stop - start;
}

/********
** mul **
*********
** Performs multiplication, modulo (2**16)+1.  This code is structured
** on the assumption that untaken branches are cheaper than taken
** branches, and that the compiler doesn't schedule branches.
*/
static uint16_t mul(register uint16_t a, register uint16_t b)
{
register uint32_t p;
if(a)
{       if(b)
	{       p=(uint32_t)(a*b);
		b=low16(p);
		a=(uint16_t)(p>>16);
		return(b-a+(b<a));
	}
	else
		return(1-a);
}
else
	return(1-b);
}

/********
** inv **
*********
** Compute multiplicative inverse of x, modulo (2**16)+1
** using Euclid's GCD algorithm.  It is unrolled twice
** to avoid swapping the meaning of the registers.  And
** some subtracts are changed to adds.
*/
static uint16_t inv(uint16_t x)
{
uint16_t t0, t1;
uint16_t q, y;

if(x<=1)
	return(x);      /* 0 and 1 are self-inverse */
t1=0x10001 / x;
y=0x10001 % x;
if(y==1)
	return(low16(1-t1));
t0=1;
do {
	q=x/y;
	x=x%y;
	t0+=q*t1;
	if(x==1) return(t0);
	q=y/x;
	y=y%x;
	t1+=q*t0;
} while(y!=1);
return(low16(1-t1));
}

/****************
** en_key_idea **
*****************
** Compute IDEA encryption subkeys Z
*/
static void en_key_idea(uint16_t *userkey, uint16_t *Z)
{
int i,j;

/*
** shifts
*/
for(j=0;j<8;j++)
	Z[j]=*userkey++;
for(i=0;j<KEYLEN;j++)
{       i++;
	Z[i+7]=(Z[i&7]<<9)| (Z[(i+1) & 7] >> 7);
	Z+=i&8;
	i&=7;
}
return;
}

/****************
** de_key_idea **
*****************
** Compute IDEA decryption subkeys DK from encryption
** subkeys Z.
*/
static void de_key_idea(IDEAkey Z, IDEAkey DK)
{
IDEAkey TT;
int j;
uint16_t t1, t2, t3;
uint16_t *p;
p=(uint16_t *)(TT+KEYLEN);

t1=inv(*Z++);
t2=-*Z++;
t3=-*Z++;
*--p=inv(*Z++);
*--p=t3;
*--p=t2;
*--p=t1;

for(j=1;j<ROUNDS;j++)
{       t1=*Z++;
	*--p=*Z++;
	*--p=t1;
	t1=inv(*Z++);
	t2=-*Z++;
	t3=-*Z++;
	*--p=inv(*Z++);
	*--p=t2;
	*--p=t3;
	*--p=t1;
}
t1=*Z++;
*--p=*Z++;
*--p=t1;
t1=inv(*Z++);
t2=-*Z++;
t3=-*Z++;
*--p=inv(*Z++);
*--p=t3;
*--p=t2;
*--p=t1;
/*
** Copy and destroy temp copy
*/
for(j=0,p=TT;j<KEYLEN;j++)
{       *DK++=*p;
	*p++=0;
}

return;
}

/*
** MUL(x,y)
** This #define creates a macro that computes x=x*y modulo 0x10001.
** Requires temps t16 and t32.  Also requires y to be strictly 16
** bits.  Here, I am using the simplest form.  May not be the
** fastest. -- RG
*/

/****************
** cipher_idea **
*****************
** IDEA encryption/decryption algorithm.
*/
static void cipher_idea(uint16_t in[4],
		uint16_t out[4],
		register IDEAkey Z)
{
register uint16_t x1, x2, x3, x4, t1, t2;
/* register uint16_t t16;
register uint16_t t32; */
int r=ROUNDS;

x1=*in++;
x2=*in++;
x3=*in++;
x4=*in;

do {
	MUL(x1,*Z++);
	x2+=*Z++;
	x3+=*Z++;
	MUL(x4,*Z++);

	t2=x1^x3;
	MUL(t2,*Z++);
	t1=t2+(x2^x4);
	MUL(t1,*Z++);
	t2=t1+t2;

	x1^=t1;
	x4^=t2;

	t2^=x2;
	x2=x3^t1;
	x3=t2;
} while(--r);
MUL(x1,*Z++);
*out++=x1;
*out++=x3+*Z++;
*out++=x2+*Z++;
MUL(x4,*Z);
*out=x4;
}