#include 
#include 
#include 


char *Encrypt(char *Data)
{
	int i;
	int Len = strlen(Data);

	if((Data == NULL) || (Len <= 0))
		return (char *)"Error Data is NULL!";

	for(i = 0; i <= Len; i++)
	{
		if(((int)toupper((int)Data[i]) >= 65) && ((int)toupper((int)Data[i]) <= 90))
		{
			Data[i] = (((toupper((int)Data[i])) + 13) % 90);

			if(Data[i] < 65)
				Data[i] += 65;
		}
	}

	return Data;
}



int main(int argc, char **argv[])
{
	char EncrText[1000];

	sprintf(EncrText, "This is a test of ROT13 Encryption");

	printf("\nThe ROT13 Cypher:\n\tThis cypher is very simple.\n\tIt simply rotates the charachters of the plaintext over 13 places.\n\n");
	printf("\nPlain Text: %s\n\n", EncrText);
	printf("Cypher Text: %s\n", Encrypt(EncrText));


	return 0;
}