Hello Kitty

It seems like a weekly occourance nowadays, whenever you turn on the news or open a technical blog you’re faced with another story where a huge organisation has been hacked and personal information has been stolen.

This time it is Hello Kitty who have lost their members’ personal information. According to wired.com more than 3.3 million user accounts have been breached. Unfortunately this is not uncommon, over the last few years we’ve heard similar stories from Sony, Ashley Madison and Experian.

What strikes me time and time again when I read these articles is how poorly my personal information is protected. Let’s look at the Hello Kitty story, wired.com tells us that users passwords were hashed with SHA1 but not salted.

Any computer science graduate or junior developer should be able to tell you that this is insufficient! I consider myself a geek so I’m always interested by this sort of thing. Let’s spend a minute to work out what’s going on…

A hash is basically a repeatable one way encryption algorithm. If you use SHA1 to hash a piece of text (such as a password) it’s trivial to repeat but (almost) mathematically impossible to work out the original string from the hashed value. This is great for developers, I save the hashed value in my database and when you enter your password I simply hash the value you gave me and see if it matches my saved version. Neither you, me or any hacker can work out what your password is even if they have somehow stolen my entire database (which I’m also protecting between DMZs, firewalls and physical security).

At first glance the security used at Hello Kitty should have been enough. Because the hackers who stole the data can’t dehash the passwords they can’t use them to log in, try them on other sites (such as your email account) you’d think this information has limited value.

This is where there’s a gaping flaw in the security and unfortunately it’s down to the users of the site. Any hacker worth their salt (pun intended) knows the most commonly used passwords. Which means I don’t need to know your password, all I need to do is hash “123456” and see which of the 3.3 million users used it. Next I try “password”, then “12345”. You won’t match everyone, but how many of these 3.3 million will use one of the top 100 most common? The top million?

So what’s the solution? We use a salt. This is what Hello Kitty should have done, a salt is a random piece of data which is appended to the password. This is often a piece of random text unique to the user which is concatenated onto the user’s password before the hashing process. This time, even if the hacker has access to the salts their lookup table of common passwords is rendered useless. They would need to calculate the top passwords with the salt for each member, a this is a hugely expensive operation and we’re back to brute force. 

Some of the most recent algorithms involve hashing a password multiple times. The effort for us to hash the hash of a password a few hundred or thousand is negligible but our hacker? They’ll have to calculate the hash of every password they want to try, for each member individually multiplied by the number of times you iterate!

I don’t want to go any further into the technical side. What I take you to take away is that somewhere, someone made a decision at Hello Kitty that a basic SHA1 hash was sufficient. That’s not only a huge error of judgement but it has ultimately left their clients feeling vulnerable as passwords are distributed across the web and has destroyed their investor confidence as the company’s reputation is dragged through the mud. Don’t let this happen to your company, don’t let this happen to your users!

Here’s my message.

  • If you’re a developer and you are not confident in your system’s security, don’t be afraid of looking foolish. Raise the questions.
  • If you are a manager who’s reportee raises a security concern, take it seriously. Your entire teams’ livelihood and clients’ confidence is at risk.
  • If you’re an Internet user, look at the common passwords list and avoid them like the plague. Use strong passwords and don’t repeat them across sites. If you don’t feel confident, don’t hand over your personal information!