iOS MD5加密

// #import <CommonCrypto/CommonDigest.h>-(NSString *)md5:(NSString *)str{    const char *cStr = [str UTF8String];    unsigned char result[16];    CC_MD5(cStr, strlen(cStr), result);    NSMutableString *hash = [NSMutableString string];    for (int i = 0; i < 16; i++)    {        [hash appendFormat:@"%02X", result[i]];    }    return [hash lowercaseString];}