iOS :MD5加密

+ (NSString *)md5:(NSString *)str{
    const char *cStr = [str UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5(cStr, strlen(cStr), result);
    return [NSString stringWithFormat:
            @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
            result[0], result[1], result[2], result[3],
            result[4], result[5], result[6], result[7],
            result[8], result[9], result[10], result[11],
            result[12], result[13], result[14], result[15]
            ]; 
}