String Encrypt

#include <string.h>

int chrpos(char *s, char c)
{
	int i = 0;
	do
	{
		if (s[i] == c) return i;
		i++;
	} while (s[i]);

	return -1;
}

void ZeroString(char *s, int len)
{
	for (int i = 0; i < len; i++) s[i] = 0x0;
}

char *StringEncrypt(char *str, char *pattern, char *key)
{
	char *temp;

	if ((strlen(str) > 0) && (strlen(pattern) > 0) && (strlen(key) > 0))
	{
		int i;
		int k = 0;
		int offset = 0;
		int pos = 0;

		temp = (char *)malloc(strlen(str) + 1);
		ZeroString(temp, strlen(str) + 1);

		for (i = 0; i < (int) strlen(str); i++)
		{
			pos = chrpos(pattern, str[i]);
			
			if (pos != -1)
			{
				offset = (int) (pos + key[k]);
				offset = offset % strlen(pattern);
				temp[i] = pattern[offset];
			}
			else
			{
				temp[i] = str[i];
			}

			k++;
			if (k >= (int) strlen(key)) k = 0;
		}
	}

	return temp;
}

char *StringDecrypt(char *str, char *pattern, char *key)
{
	char *temp;

	if ((strlen(str) > 0) && (strlen(pattern) > 0) && (strlen(key) > 0))
	{
		int i;
		int k = 0;
		int offset = 0;
		int pos = 0;

		temp = (char *)malloc(strlen(str) + 1);
		ZeroString(temp, strlen(str) + 1);

		for (i = 0; i < (int) strlen(str); i++)
		{
			pos = chrpos(pattern, str[i]);
			
			if (pos != -1)
			{
				offset = key[k] % strlen(pattern);
				offset = (int) (pos - offset);
				if (offset < 0) offset = strlen(pattern) + offset;
				temp[i] = pattern[offset];
			}
			else
			{
				temp[i] = str[i];
			}

			k++;
			if (k >= (int) strlen(key)) k = 0;
		}
	}

	return temp;
}

#define STRCRYPT_PATTERN "abcdefghijklmnopqrstuvxyzABCDEFGHIJKLMNOPQRSTUVXYZ0123456789/+-.,;?!@#$%&*()_=|<> "
#define STRCRYPT_KEY "k7&%$##Gm.<pS> (=_=)"

char *strptr = StringDecrypt(";*+OSVZ$R.(Ls-T2#B!P2Jr", STRCRYPT_PATTERN, STRCRYPT_KEY);