This is a C-style code for part of one crackme cycle.exe

cycle.c

// This is a C-style code for part of one crackme cycle.exe
// crackme download address:  http://bbs.pediy.com/attachment.php?attachmentid=503&d=1139931299
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static unsigned int dword_402182 = 0xfedcba98;

static int gather_byte_msb(unsigned int value)
{
	int ret = 0;
	int i;
	for(i = 0; i < sizeof(value); ++i){
	    ret |= ((value >> (i * 8)) & 0x80) >> (7-i);
	}
	return ret;
}

static int rol(unsigned int value, unsigned int shift)
{
    unsigned int mask;
    unsigned int high;
    if(shift > sizeof(value)*8)
        shift %= sizeof(value) * 8;
    if(shift == 0)
        return value;
    mask = ~(1 << shift);
    high = (value >> (sizeof(value)*8 - shift)) & mask;
    value = (value << shift) | high;
    return value;
}

static int ror(unsigned int value, unsigned int shift)
{
    unsigned int mask;
    unsigned int low;
    if(shift > sizeof(value)*8)
        shift %= sizeof(value)*8;
    if(shift == 0)
        return value;
    mask = ~(1 << shift);
    low = value & mask;
    value = (value >> shift) | (low << (sizeof(value)*8 - shift));
    return value;
}

static void sub_4011f1(const char *name, const char *serial, unsigned int *eax, unsigned int *ebx)
{
	int i;
	*eax = ((int *)name)[0];
	*ebx = ((int *)name)[1];

	*eax ^= ((int *)serial)[0];
	*ebx ^= ((int *)serial)[1];

	*eax &= 0x7f3f1f0f;
	*ebx &= 0x7030100;

	for(i = 0; i < 8; ++i){
		int esi = *eax;
		int edi = *ebx;
		int edx, tmp;

		esi <<= i;
		edi <<= i;

		esi = gather_byte_msb(esi);
		edi = gather_byte_msb(edi);

		edi = (esi << 4) ^ edi;

        edx = edi & 0xff;

        tmp = 8;
        if(i <= 3){
            tmp = 8 * i + 8;
            *eax = rol(*eax, tmp);
            *eax ^= edx;
            *eax = ror(*eax, tmp);
        }else{
            tmp = 8 * (i-3);
            *ebx = rol(*ebx, tmp);
            *ebx ^= edx;
            *ebx = ror(*ebx, tmp);
        }
	}
}

static void sub_401190(unsigned int *ecx, unsigned int eax, unsigned int ebx)
{
    unsigned int tmp;
    unsigned int edi, esi;
    if(*ecx <= 0x80)
        return ;
    tmp = *ecx;
    esi = *ecx;
    *ecx &= 0xff;
    if(*ecx > 8){
        edi = ebx;
        *ecx >>= 4;
    }else{
        edi = eax;
    }

    do{
        edi = rol(edi, 8);
        *ecx >>= 1;
    }while(*ecx != 0);

    esi >>= 8;
    edi &= esi;
    edi &= 0xff;

    *ecx = tmp;

restart:
    esi = 0x80;
    while(esi){
        if((esi & edi) == 0){
            esi >>= 1;
            continue;
        }
        edi ^= esi;
        *ecx &= 0xff00;
        ((char *)&esi)[1] ^= ((char *)&esi)[0];
        *ecx ^= esi;
        dword_402182++;
        sub_401190(ecx, eax, ebx);
        goto restart;
    }
}

static int verification(const char *name, const char *serial)
{
    unsigned int eax = *((int *)(&name[8]));
    unsigned int ebx = *((int *)(&name[12]));
    eax ^= ebx;

    eax ^= dword_402182;

    eax |= 0x40404040;
    eax &= 0x77777777;

    eax ^= *((int *)(&serial[8]));
    eax ^= *((int *)(&serial[12]));

    if(eax == 0){
        printf("[!] name and serial number passed !\n");
    }else{
        printf("[*] name and serial number failed !\n");
    }
}

#define NAME_LEN    16
#define BUFFSIZE    (NAME_LEN + 1)      // one for terminate character
static void fullfill_name(char *name, size_t size)
{
    int i;
    size_t len = strlen(name) - 1;         // one for '\n' character
    for(i = 0; i < size-len; ++i){
        name[i+len] = name[i];
    }
    name[size] = '\0';
}

int main(void)
{
    //char name[BUFFSIZE];
	unsigned int eax, ebx;
	unsigned int ecx = 0xff01;
	const char *name = "litao3rdlitao3rd";
	const char *serial = "123456782332ASaA";
	#if 0
	fgets(name, BUFFSIZE, stdin);
	fullfill_name(name, NAME_LEN);
	#endif // 0

	sub_4011f1(name, serial, &eax, &ebx);
    sub_401190(&ecx, eax, ebx);
    if(ecx != 1){
        fprintf(stderr, "sub_401190 failure! ecx = %#x\n", ecx);
        exit(-1);
    }
    verification(name, serial);

	return 0;
}