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I am curious about how do you protect your software against cracking, hacking etc.
Do you employ some kind of serial number check? Hardware keys?
Do you use any third-party solutions?
How do you go about solving licensing issues? (e.g. managing floating licenses)
EDIT: I'm not talking any open source, but strictly commercial software distribution...
There are many, many, many protections available. The key is:
Assessing your target audience, and what they're willing to put up with
Understanding your audience's desire to play with no pay
Assessing the amount someone is willing to put forth to break your protection
Applying just enough protection to prevent most people from avoiding payment, while not annoying those that use your software.
Nothing is unbreakable, so it's more important to gauge these things and pick a good protection than to simply slap on the best (worst) protection you are able to afford.
Simple registration codes (verified online once).
Simple registration with revokable keys, verified online frequently.
Encrypted key holds portion of program algorithm (can't just skip over the check - it has to be run for the program to work)
Hardware key (public/private key cryptography)
Hardware key (includes portion of program algorithm that runs on the key)
Web service runs critical code (hackers never get to see it)
And variations of the above.
Whatever route you go, charge a fair price, make it easy to activate, give free minor updates and never deactivate their software. If you treat your users with respect they'll reward you for it. Still, no matter what you do some people are going to end up pirating it.
Don't.
Pirates will pirate. No matter what solution you come up with, it can and will be cracked.
On the other hand, your actual, paying customers are the ones who are being inconvenienced by the crap.
Make it easier to buy than to steal. If you put mounds of copy protection then it just makes the value of owning the real deal pretty low.
Use a simple activation key and assure customers that they can always get an activation key or re-download the software if they ever lose theirs.
Any copy protection (aside from online-only components like multiplayer games and finance software that connects to your bank, etc.) you can just assume will be defeated. You want downloading your software illegally, at the very least, to be slightly harder than buying it.
I have a PC games that I've never opened, because there is so much copy protection junk on it that it's actually easier to download the fake version.
Software protections aren't worth the money -- if your software is in demand it will be defeated, no matter what.
That said, hardware protections can work well. An example way it can work well is this: Find a (fairly) simple but necessary component of your software and implement it in Verilog/VHDL. Generate a public-private keypair and make a webservice that takes a challenge string and encrypts it with the private key. Then make a USB dongle that contains your public key and generates random challenge strings. Your software should ask the USB dongle for a challenge string and send it up to the server for encryption. The software then sends it to the dongle. The dongle validates the encrypted challenge string with the public key and goes into an 'enabled' mode. Your software then calls into the dongle any time it needs to do the operation you wrote in HDL. This way anyone wanting to pirate your software has to figure out what the operation is and reimplement it -- much harder than just defeating a pure software protection.
Edit: Just realized some of the verification stuff is backwards from what it should be, but I'm pretty sure the idea comes across.
The Microsoft Software License scheme is crazy expensive for a small business. The server cost is around $12,000 if you want to set it up yourself. I don't recommend it for the feint of heart.
We actually just implemented Intellilock in our product. It lets you have all of the decisions for how strict you want your license to be, and it is very cost effective as well. In addition it does obfuscation, compiler prevention, etc.
Another good solution I have seen small/med businesses use is SoloServer. It is much more of an ecommerce and license control system. It is very configurable to the point of maybe a little too complex. But it does a very good job from what I have heard.
I have also used the Desaware license system for dot net in the past. It is a pretty lightweight system compared to the two above. It is a very good license control system in terms of cryptographically sound. But it is a very low level API in which you have to implement almost everything your app will actually use.
Digital "Rights" Management is the single biggest software snake-oil product in the industry. To borrow a page from classic cryptography, the typical scenario is that Alice wants to get a message to Bob without Charlie being able to read it. DRM doesn't work because in its application, Bob and Charlie are the same person!
You would be better off asking the inverse question, which is "How do I get people to buy my software instead of stealing it?" And that is a very broad question. But it generally starts by doing research. You figure out who buys the type of software you wish to sell, and then produce software that appeals to those people.
The additional prong to this is to limit updates/add-ons to legit copies only. This can be something as simple as an order code received during the purchase transaction.
Check out Stardock software, makers of WindowBlinds and games such as Sins of a Solar Empire, the latter has no DRM and turned a sizable profit off a $2M budget.
There are several methods, such as using the processor ID to generate an "activation key."
The bottom line is that if someone wants it bad enough -- they'll reverse engineer any protection you have.
The most failsafe methods are to use online verification at runtime or a hardware hasp.
Good luck!
Given a little time your software will always be cracked. You can search for cracked versions of any well known piece of software in order to confirm this. But it is still well worth adding some form of protection to your software.
Remember that dishonest people will never pay for your software and always find/use a cracked version. Very honest people will always stick to the rules even without a licensing scheme just because that is the kind of person they are. But the majority of people are between these two extremes.
Adding some simple protection scheme is a good way of making that bulk of people in the middle act in an honest way. It is a way to nudge them into remembering that the software is not free and they should be paying for the appropriate number of licenses. Many people do actually respond to this. Businesses are especially good at sticking to the rules because the manager is not spending his/her own money. Consumers are less likely to stick to the rules because it is their own money.
But recent experience with releases such as Spore from Electronic Arts shows that you can go to far in licensing. If you make even legit people feel like criminals because they are constantly being validated then they start to rebel. So add some simple licensing to remind people if they are being dishonest but anything more than that is unlikely to boost sales.
Online-only games like World of Warcraft (WoW) have it made, everyone has to connect to the server every time and thus accounts can be constantly verified. No other method works for beans.
Generally there are two systems that often get confused -
Licensing or activation tracking, legal legitimate usage
Security preventing illegal usage
For licensing use a commercial package, FlexLM many companies invest huge sums of money into licensing think they also get security, this is a common mistake key generators for these commercial packages are prolifically abundant.
I would only recommend licensing if your selling to corporations who will legitimately pay based on usage, otherwise its probably more effort than its worth.
Remember that as your products become successful, all and every licensing and security measure will be breached eventually. So decide now if it is really worth the effort.
We implemented a clean room clone of FlexLM a number of years ago, we also had to enhance our applications against binary attacks, its long process, you have to revisit it every release. It also really depends on which global markets you sell too, or where your major customer base is as to what you need to do.
Check out another of my answers on securing a DLL.
As has been pointed out, software protection is never guaranteed to be foolproof. What you intend to use depends largely on your target audience. A game, for instance, is not something you are going to be able to protect forever. A server software, on the other hand, is something far less likely to be distributed on the Internet, for a number of reasons (product penetration and liability come to mind; a large corporation does not want to be held liable for bootleg software, and the pirates only bother with things in large-enough demand). In all honesty, for a high-profile game, the best solution is probably to seed the torrent yourself (clandestinely!) and modify it in some way (for instance, so that after two weeks of play it pops up with messages telling you to please consider supporting the developers by purchasing a legitimate copy).
If you put protection in place, bear two things in mind. First, a lower price will supplement any copy protection by making people more inclined to pay the purchase price. Secondly, the protection must not get in the way of users - see Spore for a recent example.
DRM this, DRM that - publishers who force DRM on their projects are doing it because it's profitable. Their economists are concluding this on data which none of us will ever see. The "DRM is evil" trolls are going a little too far.
For a low-visibility product, a simple internet activation is going to stop casual copying. Any other copying is likely negligible to your bottom line.
Illegal distribution is practically impossible to prevent; just ask the RIAA. Digital content can just be copied; analog content can be digitised, and then copied.
You should focus your efforts on preventing unauthorised execution. It's never possible to completely prevent the execution of code on someone else's machine, but you can take certain steps to raise the bar sufficiently high that it becomes easier to purchase your software than to pirate it.
Take a look at the article Developing for Software Protection and Licensing that explains how best to go about developing your application with licensing in mind.
Obligatory disclaimer & plug: the company I co-founded produces the OffByZero Cobalt software licensing solution for .NET.
The trouble with this idea of just let the pirates use it they wont buy it anyway and will show their friends who might buy it is twofold.
With software that uses 3rd party services, the pirated copies are using up valuable bandwidth/resource which gives legit users a worse experience, make my sw look more popular then it is and has the 3rd party services asking me to pay more for their services because of the bandwidth being used.
Many casual wouldn't dream of cracking the sw themselves but if there is an easy assessible crack on a site like piratebay they will use it, if there wasn't they might buy it.
This concept of not disabling pirated software once discovered also seems crazy, I don't understand why I should let someone continue to use software they shouldn't be using, I guess this is just the view/hope of the pirates.
Also, its worth noting that making a program hard to crack is one thing, but you also need to prevent legit copies being shared, otherwise somebody could simply buy one copy and then
share it with thousands of others via a torrent site. The fact of having their name/email address embedded in the license isn't going to be enough to disuade everyone from doing this, and it only really takes one for there to be a problem.
The only way I can see to prevent this is to either:
Have server check and lock license on program startup every time, and release license on program exit. If another client starts with same license whilst the first client has license then it is rejected. This way doesn't prevent the license being used by more than one user, but does prevent it being used concurrently by more than one user - which is good enough. It also allows a legitimate user to transfer the license on any of their computers which provides a better experience.
On first client startup client sends license to server and server verifies it, causing some flag to be set within the client software. Further requests from other clients with the same license are rejected. The trouble with this approach is the original client would have problems if they reinstalled the software or wanted to use a different computer.
Even if you used some kind of biometric fingerprint authentication, someone would find a way to crack it. There's really no practical way around that. Instead of trying to make your software hack-proof, think about how much extra revenue will be brought in by adding additional copy protection vs. the amount of time and money it will take to implement it. At some point, it gets to be cheaper to go with a less rigorous copy protection scheme.
It depends on what exactly your software product is, but one possibility is to move the "valuable" part of the program out of the software and keep it under your exclusive control. You would charge a modest fee for the software (mostly to cover print and distribution costs) and would generate your revenue from the external component. For example, an anti-virus program that is sold for cheap (or bundled for free with other products) but sells subscriptions to its virus definitions update service. With that model, a pirated copy that subscribes to your update service wouldn't represent much of a financial loss. With the increasing popularity of applications "in the cloud", this method is becoming easier to implement; host the application on your cloud, and charge users for cloud access. This doesn't stop someone from re-implementing their own cloud to eliminate the need for your service, but the time and effort involved in doing so would most likely outweigh the benefits (if you keep your pricing model reasonable).
If your interested in protecting software that you intend to sell to consumers I would recommend any of a variety of license key generating libraries (Google search on license key generation). Usually the user has to give you some sort of seed like their email address or name and they get back the registration code.
Several companies will either host and distribute your software or provide a complete installation/purchase application that you can integrate with and do this automatically probably at no additional cost to you.
I have sold software to consumers and I find this the right balance of cost/ease of use/protection.
The simple, and best solution, is just to charge them up front. Set a price that works for you and them.
Asking paying customers to prove that they are paying customers after they've already paid just pisses them off. Implementing the code to make your software not run wastes your time and money, and introduces bugs and annoyances for legitimate customers. You'd be better off spending that time making a better product.
Lots of games/etc will "protect" the first version, then drop the protections in the first patch due to compatibility problems with real customers. It's not an unreasonable strategy if you insist on a modicum of protection.
Almost all copy-protection is both ineffective, and a usability nightmare. Some of it, such as putting root-kits on your customers' machines becomes downright unethical
I suggest simple activation key (even if you know that it can be broken), you really don't want your software to get in your users way, or they'll simply push it away.
Make sure that they can re-download the software, I suggest a web page where they can logging and download your software only after they paid (and yes they should be able to download as many times they wish it, directly, without a single question about why on your part).
Thrust your paid users above all, there is nothing more irritating that being accused from being a criminal when you are a legit users (DVD's anti-piracy warnings anyone).
You can add a service that checks the key against a server when online, and in case of two different IPs are using the same key, popup a suggestion to buy another license.
But please don't inactivate it, it might be a happy user showing your software to a friend!!!!
Make part of your product an online component which requires connection and authentication. Here are some examples:
Online Games
Virus Protection
Spam Protection
Laptop tracking software
This paradigm only goes so far though and can turn some consumers off.
I agree with a lot of posters that no software-based copy protection scheme will deter against a skilled software pirate. For commercial .NET based software Microsoft Software License Protection (SLP) is a very reasonably priced solution. It supports time-limited and floating licenses. Their pricing starts at $10/month + $5 per activation and the protection components seem to work as advertised. It's a fairly new offering, though, so buyer beware.
Related
I've been involved in a discussion about how to build internet voting software for a general election. We've reached a general consensus that there exist plenty of secure methods for two way authentication and communication.
However, someone came along and pointed out that in a general election some of the machines being used are almost certainly going to be compromised. To quote:
Let me be an evil electoral fraudster.
I want to sample peoples votes as they
vote and hope I get something
scandalous. I hire a bot-net from some
really shady dudes who control 1000
compromised machines in the UK just
for election day.
I capture the voting habits of 1000
voters on election day. I notice 5 of
them have voted BNP. I look these
users up and check out their machines,
I look through their documents on
their machine and find out their names
and addresses. I find out one of them
is the wife of a tory MP. I leak 'wife
of tory mp is a fascist!' to some
blogger I know. It hits the internet
and goes viral, swings an election.
That's a serious problem!
So, what are the best techniques for running software where user interactions with the software must be kept secret, on a machine which is possibly compromised?
It can't be done. Fortunately, banks face exactly the same problem, so those little home chip'n'pin doohickies are pretty cheap.
So, if you want secure online voting, you send a custom voting doohicky to everyone who applies for one. This doohicky signs and encrypts their vote before sending it to the PC to be transmitted over the wire. The only thing an attacker on the wire can do, is eavesdrop whether or not the voter voted at all. Since political parties already do this, by posting party workers outside polling stations, that's not a significant risk to the system ;-)
You still face some of the problems of postal voting, such as vote buying and coercion, or stealing someone's doohicky, but only via physical access, not by compromising their PC. There's obvious DOS attacks if you rely on home internet connections, but there's no reason the voter can't have the option of going to the polling station if their connection goes down.
Whether the doohicky is cheap enough is still doubtful - I guess they cost a few pounds each, which I don't think is cheap on the scale of what is actually spent on elections. But they're not infeasibly expensive. I doubt they save much money at polling stations, unfortunately. The cost of polling in the UK depends pretty much on the number of polling stations. Problems this time notwithstanding, the number of polling stations isn't driven by the need to provide a fast enough throughput, it's driven by a desire that people not have to travel far to get to them. So having fewer voters doesn't really allow you to reduce the number of polling stations. Reducing paper might save time and money at the count, but surely not enough to pay for doohickies.
Finally of course there's still a risk of attack on the hardware. Someone could maybe intercept them in the post and replace them with identical-looking devices. But unlike attacking the hardware at a polling station, the attacker only affects one vote per piece of dedicated voting hardware compromised, so at least the bar is set high to begin with.
So, what are the best techniques for running software where user interactions with the software must be kept secret, on a machine which is possibly compromised?
The only answer is that you cannot / must not do it. If the hardware or OS might have been compromised you cannot guarantee to keep the user interactions secret.
But the other take on this is that no voting system known to mankind (electronic or otherwise) is incorruptible. That is why you need to have people checking for fraud, and people watching the people, and a culture where corrupt behavior is not the norm.
EDIT
... if one can reduce the impact of compromised machines to below the level of corruption in a paper voting system you're achieving a positive gain.
You also have to take into account other forms of corruption that are much easier with electronic voting from home. Like stand-over tactics, votes for sale, the fact that most people do not properly protect their electronic credentials, etc). In short, what you are proposing is hypothetical, and (IMO) unrealistic.
It is simpler to fix the flaws with in-person, on-paper voting than to address a whole bunch of potentially worse problems with a hypothetical from-home, electronic voting.
(Also, you are implying a level of corruption with UK paper voting that surprises me as an ex UK resident. This is off topic, but can you provide references / links that back this up?)
You have two main choices, either sidestep the comprimized part of the machine (e.g. provide the full OS) or work within the comprimise and make it hard to get hold of the data.
The second choice is more practical. Although you can't stop the shady dudes from eventually getting the data, you can make it difficult enough that it will take longer than a day, rendring the leaked voting habits harmless.
Assuming a web application, not using standard UI components and varying their locations on the screen, using multiple layers of encryption, disabling keyboard input, and using animations to fool screen grabbers can all make the process tricker to buy more time.
Obviously you can not ensure confidentiality of the vote if the machine the vote is entered with is compromised. Whatever measures you take, all an attacker needs to do is to execute your software in a virtual machine that records all access to keyboard, mouse and screen. By playing back the recording, the attacker can see how the user voted ...
However, when designing a E-Voting protocol this is the least of your worries. How do you prevent somebody from hacking the election server and manipulating results? How do you even detect tampering? What about the secrecy of my vote if the server is compromised? Can I be forced to reveal my vote?
The biggest threat facing e-voting is the ability for an attacker to influence the election. By spending CD's to people you make Massive Identity Leaks more valuable. Not only can an attacker destroy their credit, but they can also destroy their country.
Even forcing people to use specific hardware doesn't work. Look at console modding, or ATM Skimmers and Hardware Keyloggers. You have to worry about transferring the votes to be counted, even SSL has secuirty problems. There are also the problem of the centralized database, sql injection would be devastating.
The real question is, "Is e-voting more secure than paper voting?" What is harder for an attacker to influence? To be honest I don't think e-voting machines would have changed the outcome of the recent Iranian election.
An obvious solution is to send the software to the end user on a bootable CD. The user simply restarts their computer and they're now on a non compromised computer.
However, this is not terribly simple to develop (trying to make the OS on the CD compatible with all the variations of hardware we're going to encounter on machines). Also, I can't imagine that the average home user has their BIOS set to "Boot from CD" and telling voters to modify their BIOS settings is just going to far.
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I am an IT student and I am now in the 3rd year in university. Until now we've been studing a lot of subjects related to computers in general (programming, algorithms, computer architecture, maths, etc).
I am very sure that nobody can learn every thing about security but sure there is a "minimum" knowledge every programmer or IT student should know about it and my question is what is this minimum knowledge?
Can you suggest some e-books or courses or anything can help to start with this road?
Principles to keep in mind if you want your applications to be secure:
Never trust any input!
Validate input from all untrusted sources - use whitelists not blacklists
Plan for security from the start - it's not something you can bolt on at the end
Keep it simple - complexity increases the likelihood of security holes
Keep your attack surface to a minimum
Make sure you fail securely
Use defence in depth
Adhere to the principle of least privilege
Use threat modelling
Compartmentalize - so your system is not all or nothing
Hiding secrets is hard - and secrets hidden in code won't stay secret for long
Don't write your own crypto
Using crypto doesn't mean you're secure (attackers will look for a weaker link)
Be aware of buffer overflows and how to protect against them
There are some excellent books and articles online about making your applications secure:
Writing Secure Code 2nd Edition - I think every programmer should read this
Building Secure Software: How to Avoid Security Problems the Right Way
Secure Programming Cookbook
Exploiting Software
Security Engineering - an excellent read
Secure Programming for Linux and Unix HOWTO
Train your developers on application security best pratices
Codebashing (paid)
Security Innovation(paid)
Security Compass (paid)
OWASP WebGoat (free)
Rule #1 of security for programmers: Don't roll your own
Unless you are yourself a security expert and/or cryptographer, always use a well-designed, well-tested, and mature security platform, framework, or library to do the work for you. These things have spent years being thought out, patched, updated, and examined by experts and hackers alike. You want to gain those advantages, not dismiss them by trying to reinvent the wheel.
Now, that's not to say you don't need to learn anything about security. You certainly need to know enough to understand what you're doing and make sure you're using the tools correctly. However, if you ever find yourself about to start writing your own cryptography algorithm, authentication system, input sanitizer, etc, stop, take a step back, and remember rule #1.
Every programmer should know how to write exploit code.
Without knowing how systems are exploited you are accidentally stopping vulnerabilities. Knowing how to patch code is absolutely meaningless unless you know how to test your patches. Security isn't just a bunch of thought experiments, you must be scientific and test your experiments.
Security is a process, not a product.
Many seem to forget about this obvious matter of fact.
I suggest reviewing CWE/SANS TOP 25 Most Dangerous Programming Errors. It was updated for 2010 with the promise of regular updates in the future. The 2009 revision is available as well.
From http://cwe.mitre.org/top25/index.html
The 2010 CWE/SANS Top 25 Most Dangerous Programming Errors is a list of the most widespread and critical programming errors that can lead to serious software vulnerabilities. They are often easy to find, and easy to exploit. They are dangerous because they will frequently allow attackers to completely take over the software, steal data, or prevent the software from working at all.
The Top 25 list is a tool for education and awareness to help programmers to prevent the kinds of vulnerabilities that plague the software industry, by identifying and avoiding all-too-common mistakes that occur before software is even shipped. Software customers can use the same list to help them to ask for more secure software. Researchers in software security can use the Top 25 to focus on a narrow but important subset of all known security weaknesses. Finally, software managers and CIOs can use the Top 25 list as a measuring stick of progress in their efforts to secure their software.
A good starter course might be the MIT course in Computer Networks and Security. One thing that I would suggest is to not forget about privacy. Privacy, in some senses, is really foundational to security and isn't often covered in technical courses on security. You might find some material on privacy in this course on Ethics and the Law as it relates to the internet.
The Web Security team at Mozilla put together a great guide, which we abide by in the development of our sites and services.
The importance of secure defaults in frameworks and APIs:
Lots of early web frameworks didn't escape html by default in templates and had XSS problems because of this
Lots of early web frameworks made it easier to concatenate SQL than to create parameterized queries leading to lots of SQL injection bugs.
Some versions of Erlang (R13B, maybe others) don't verify ssl peer certificates by default and there are probably lots of erlang code that is susceptible to SSL MITM attacks
Java's XSLT transformer by default allows execution of arbitrary java code. There has been many serious security bugs created by this.
Java's XML parsing APIs by default allow the parsed document to read arbitrary files on the filesystem. More fun :)
You should know about the three A's. Authentication, Authorization, Audit. Classical mistake is to authenticate a user, while not checking if user is authorized to perform some action, so a user may look at other users private photos, the mistake Diaspora did. Many, many more people forget about Audit, you need, in a secure system, to be able to tell who did what and when.
Remember that you (the programmer) has to secure all parts, but the attacker only has to succeed in finding one kink in your armour.
Security is an example of "unknown unknowns". Sometimes you won't know what the possible security flaws are (until afterwards).
The difference between a bug and a security hole depends on the intelligence of the attacker.
I would add the following:
How digital signatures and digital certificates work
What's sandboxing
Understand how different attack vectors work:
Buffer overflows/underflows/etc on native code
Social engineerring
DNS spoofing
Man-in-the middle
CSRF/XSS et al
SQL injection
Crypto attacks (ex: exploiting weak crypto algorithms such as DES)
Program/Framework errors (ex: github's latest security flaw)
You can easily google for all of this. This will give you a good foundation.
If you want to see web app vulnerabilities, there's a project called google gruyere that shows you how to exploit a working web app.
when you are building any enterprise or any of your own software,you should just think like a hacker.as we know hackers are also not expert in all the things,but when they find any vulnerability they start digging into it by gathering information about all the things and finally attack on our software.so for preventing such attacks we should follow some well known rules like:
always try to break your codes(use cheatsheets & google the things for more informations).
be updated for security flaws in your programming field.
and as mentioned above never trust in any type of user or automated inputs.
use opensource applications(their most security flaws are known and solved).
you can find more security resource on the following links:
owasp security
CERT Security
SANS Security
netcraft
SecuritySpace
openwall
PHP Sec
thehackernews(keep updating yourself)
for more information google about your application vendor security flows.
Why is is important.
It is all about trade-offs.
Cryptography is largely a distraction from security.
For general information on security, I highly recommend reading Bruce Schneier. He's got a website, his crypto-gram newsletter, several books, and has done lots of interviews.
I would also get familiar with social engineering (and Kevin Mitnick).
For a good (and pretty entertaining) book on how security plays out in the real world, I would recommend the excellent (although a bit dated) 'The Cuckoo's Egg' by Cliff Stoll.
Also be sure to check out the OWASP Top 10 List for a categorization of all the main attack vectors/vulnerabilities.
These things are fascinating to read about. Learning to think like an attacker will train you of what to think about as you're writing your own code.
Salt and hash your users' passwords. Never save them in plaintext in your database.
Just wanted to share this for web developers:
security-guide-for-developershttps://github.com/FallibleInc/security-guide-for-developers
I've been asked to develop a key generation/validation system for some software. They would also be open to a developed open source or commercial system, but would prefer a system from scratch. Online activation would have to optional, since it is likely that some installations would be on isolated servers. I know there is kind of a user/security complex with a lot of anit-piracy techniques. So I guess I'm asking what software, libraries, and techniques are out there? I would appreciate personal knowledge, web sites, or books.
If you take the hash of something, it will result (ideally) in an unpredictable string of characters.
You could have an algorithm be to take the SHA1 of something predictable (like sequential numbers) concatenated with a sufficiently long salt. Your keys would be really secure as long as your salt remains a permanent secret and SHA1 is never breached.
For example, if you take the SHA1 of "1" (your first license key) and a super secret salt "stackoverflow8as7f98asf9sa78f7as9f87a7", you get the key "95d78a6331e01feca457762a092bdd4a77ef1de1". You could prepend this with version numbers if you want.
If you want online authorization, you need three things:
To ensure that the response cannot be forged
To ensure that the request cannot be forged
To ensure that if Internet is unavailable, you take appropriate action
Public key cryptography can help with items one and two. Even Photoshop CS4 has problems with item 3, that's a tricky one.
I'm biased - given that the company I co-founded developed the Cobalt software licensing solution for .NET - but I'd suggest you go with a third-party solution rather than rolling your own.
Take a look at the article Developing for Software Protection and Licensing, which makes the following point:
We believe that most companies would
be better served by buying a
high-quality third-party licensing
system. This approach will free your
developers to work on core
functionality, and will alleviate
maintenance and support costs. It also
allows you to take advantage of the
domain expertise offered by licensing
specialists, and avoid releasing
software that is easy to crack.
Another advantage to buying a
third-party solution is that you can
quickly and easily evaluate it for
suitability; with an in-house system
you have to pay in advance for the
development of a system that may not
prove adequate for your needs.
Choosing an high-quality third party
system dramatically reduces the risk
involved in developing a solution
in-house.
If you're dead set on rolling your own, a word of advice: test on the widest range of client systems possible. Real-world hardware is weird, and Windows behaviour varies quite dramatically in some ways between versions.
You'll almost certainly have to spend a lot of time ironing the creases out of whatever hardware identification system you implement.
There's a lot of security advice out there to tell programmers what not to do. What in your opinion are the best practices that should be followed when coding for good security?
Please add your suggested security control / design pattern below. Suggested format is a bold headline summarising the idea, followed by a description and examples e.g.:
Deny by default
Deny everything that is not explicitly permitted...
Please vote up or comment with improvements rather than duplicating an existing answer. Please also put different patterns and controls in their own answer rather than adding an answer with your 3 or 4 preferred controls.
edit: I am making this a community wiki to encourage voting.
Principle of Least Privilege -- a process should only hold those privileges it actually needs, and should only hold those privileges for the shortest time necessary. So, for example, it's better to use sudo make install than to su to open a shell and then work as superuser.
All these ideas that people are listing (isolation, least privilege, white-listing) are tools.
But you first have to know what "security" means for your application. Often it means something like
Availability: The program will not fail to serve one client because another client submitted bad data.
Privacy: The program will not leak one user's data to another user
Isolation: The program will not interact with data the user did not intend it to.
Reviewability: The program obviously functions correctly -- a desirable property of a vote counter.
Trusted Path: The user knows which entity they are interacting with.
Once you know what security means for your application, then you can start designing around that.
One design practice that doesn't get mentioned as often as it should is Object Capabilities.
Many secure systems need to make authorizing decisions -- should this piece of code be able to access this file or open a socket to that machine.
Access Control Lists are one way to do that -- specify the files that can be accessed. Such systems though require a lot of maintenance overhead. They work for security agencies where people have clearances, and they work for databases where the company deploying the database hires a DB admin. But they work poorly for secure end-user software since the user often has neither the skills nor the inclination to keep lists up to date.
Object Capabilities solve this problem by piggy-backing access decisions on object references -- by using all the work that programmers already do in well-designed object-oriented systems to minimize the amount of authority any individual piece of code has. See CapDesk for an example of how this works in practice.
DARPA ran a secure systems design experiment called the DARPA Browser project which found that a system designed this way -- although it had the same rate of bugs as other Object Oriented systems -- had a far lower rate of exploitable vulnerabilities. Since the designers followed POLA using object capabilities, it was much harder for attackers to find a way to use a bug to compromise the system.
White listing
Opt in what you know you accept
(Yeah, I know, it's very similar to "deny by default", but I like to use positive thinking.)
Model threats before making security design decisions -- think about what possible threats there might be, and how likely they are. For, for example, someone stealing your computer is more likely with a laptop than with a desktop. Then worry about these more probable threats first.
Limit the "attack surface". Expose your system to the fewest attacks possible, via firewalls, limited access, etc.
Remember physical security. If someone can take your hard drive, that may be the most effective attack of all.
(I recall an intrusion red team exercise in which we showed up with a clipboard and an official-looking form, and walked away with the entire "secure" system.)
Encryption ≠ security.
Hire security professionals
Security is a specialized skill. Don't try to do it yourself. If you can't afford to contract out your security, then at least hire a professional to test your implementation.
Reuse proven code
Use proven encryption algorithms, cryptographic random number generators, hash functions, authentication schemes, access control systems, rather than rolling your own.
Design security in from the start
It's a lot easier to get security wrong when you're adding it to an existing system.
Isolation. Code should have strong isolation between, eg, processes in order that failures in one component can't easily compromise others.
Express risk and hazard in terms of cost. Money. It concentrates the mind wonderfully.
Well understanding of underlying assumptions on crypto building blocks can be important. E.g., stream ciphers such as RC4 are very useful but can be easily used to build an insecure system (i.e., WEP and alike).
If you encrypt your data for security, the highest risk data in your enterprise becomes your keys. Lose the keys, and data is lost; compromise the keys and all your data is compromised.
Use risk to make security decisions. Once you determine the probability of different threats, then consider the harm that each could do. Risk is, by definition
R = Pe × H
where Pe is the probability of the undersired event, and H is the hazard, or the amount of harm that could come from the undesired event.
Separate concerns. Architect your system and design your code so that security-critical components can be kept together.
KISS (Keep It Simple, Stupid)
If you need to make a very convoluted and difficult to follow argument as to why your system is secure, then it probably isn't secure.
Formal security designs sometimes refer to a thing called the TCB (Trusted Computing Base). But even an informal design has something like this - the security enforcing part of your code, the part you can't avoid relying on. This needs to be well encapsulated and as simple and small as possible.
What is the best way to avoid that an application is copied and used without the owner’s knowing?
Is there any way to trace the usage? Meaning periodically the application communicates back, with enough information so that we can know where it is, and if it’s legal. Next thing, of course, shut it down, if it’s not legit.
Software that "phones home" will be quickly shunned by the vast majority of your users. Just license it appropriately and sell it.
People who use your software professionally will either pay for it or they won't use it. Corporations tend to frown on potential lawsuits.
People who want to use your software without paying for it will continue to do so despite your best efforts to counteract them. Once the software is in their hands, it is out of yours. Without pissing off your users, your only recourse is a legal one.
If your product is priced reasonably, some people will pay for it and some won't. That is just something you need to deal with upfront and it should be factored into your business plan.
Don't do this, don't attempt it, don't even think about it.
This is a battle you can't win. If people want to pirate your software they will. You'll be shamed by the fact that a smart reverse engineer can write a one byte binary patch to subvert all your protection schemes.
The people who are going to pirate your software will do so and all these "security features" you build in will likely end up only inconveniencing your true supporters: the people who have legitimately purchased your software. These draconian DRM / anti-piracy schemes only build resentment among software users.
Hardware dongles are the best way if you are really concerned about piracy IMO. Check out the big industrial CAD/CAM packages worth thousands or tens-of-thousands, or the AV/Music production software, they virtually all have dongle protection. Dongles can be emulated or reversed but not without a significant investment in time, a lot more than just changing a few JEs to JNEs in your assembly.
Phoning home is not the way to go unless you are providing a service that requires a subscription and constant updates (like antivirus products, for example) as part of your business model. You need to have a bit of respect for your users and their privacy. You might have perfectly innocent intentions but what if a court ordered your company to hand over that information (like the US government is doing with Google and its search terms) - would/could you fight it? What if you some time in the future sold your company and the new owners decided to sell all that historic information to a marketing company? Privacy is not just about trusting a company not to abuse your data, it is trusting that company to go out of their way to protect your data. Which is pretty far down the list of priorities for most companies. So basically, the monitoring users thing is not really a good path to go down.
The best (and pretty much only) way to reliably prevent piracy is to have a client/server application instead of a standalone one, where a non-trivial part of the work is done by the server and users need to register. Then you can at least detect and block simultaneous use of the same account.
There are several approaches you could take, but there are three that will be vastly more effective that any of the others.
A. Don't create it.
Software that doesn't exist never suffers from unauthorized use.
B. Don't release it.
If you have the only copy, and you keep it that way, then the chances are exceedingly good that there will be no unauthorized use.
C. Give everyone permission to use it.
If you don't want anyone to use it without permission, then you can give everyone permission and there will be no unauthorized users.
There is a possibility to trace the usage. You can accomplish this by letting phone your tool home and send the information you need. The problem with this is, that first nobody likes software that phones home for this purpose and second with a simple application-level gateway you can block the application to phone home! What you describe in your question is a common problem of software-distributors and it's not an easy one to solve!
There's another thing I haven't seen mentioned yet : You could add loads of settings to the applications' configuration file, and start with ridiculous defaults. Then do the installation & configuration personally, so no-one but you is able to figure out how everything should be set. This can be a mayor put-down for people that are just trying out if a copy is enough. (Be sure to add settings that depend on all sorts of system-settings, like OS-version related DLL-versions that should be loaded, etc). Not very user-friendly tho ;-)