Practical Public Key Cryptography

October 18, 2017 by Pedro Umbelino 25 Comments

Encryption is one of the pillars of modern-day communications. You have devices that use encryption all the time, even if you are not aware of it. There are so many applications and systems using it that it’s hard to begin enumerating them. Ranging from satellite television to your mobile phone, from smart power meters to your car keys, from your wireless router to your browser, and from your Visa to your Bitcoins — the list is endless.

One of the great breakthroughs in the history of encryption was the invention of public key cryptography or asymmetrical cryptography in the 70’s. For centuries traditional cryptography methods were used, where some secret key or scheme had to be agreed and shared between the sender and the receiver of an encrypted message.

Asymmetric cryptography changed that. Today you can send an encrypted message to anyone. This is accomplished by the use of a pair of keys: one public key and one private key. The key properties are such that when something is encrypted with the public key, only the private key can decrypt it and vice-versa. In practice, this is usually implemented based on mathematical problems that admit no efficient solution like certain integer factorization, discrete logarithm and elliptic curve relationships.

But the game changer is that the public key doesn’t have to be kept secret. This allows cryptography to be used for authentication — proving who someone is — as well as for encryption, without requiring you to have previously exchanged secrets. In this article, I’ll get into the details of how to set yourself up so that anyone in the world is able to send you an e-mail that only you can read.
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Bad RSA Library Leaves Millions Of Keys Vulnerable

October 17, 2017 by Pedro Umbelino 20 Comments

So, erm… good news everyone! A vulnerability has been found in a software library responsible for generating RSA key pairs used in hardware chips manufactured by Infineon Technologies AG. The vulnerability, dubbed ROCA, allows for an attacker, via a Coppersmith’s attack, to compute the private key starting with nothing more than the public key, which pretty much defeats the purpose of asymmetric encryption altogether.

Affected hardware includes cryptographic smart cards, security tokens, and other secure hardware chips produced by Infineon Technologies AG. The library with the vulnerability is also integrated in authentication, signature, and encryption tokens of other vendors and chips used for Trusted Boot of operating systems. Major vendors including Microsoft, Google, HP, Lenovo, and Fujitsu already released software updates and guidelines for mitigation.

The researchers found and analysed vulnerable keys in various domains including electronic citizen documents (750,000 Estonian identity cards), authentication tokens, trusted boot devices, software package signing, TLS/HTTPS keys and PGP. The currently confirmed number of vulnerable keys found is about 760,000 but could be up to two to three orders of magnitude higher.

Devices dating back to at least 2012 are affected, despite being NIST FIPS 140-2 and CC EAL 5+ certified.. The vulnerable chips were not necessarily sold directly by Infineon Technologies AG, as the chips can be embedded inside devices of other manufacturers.

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Aussies Propose Crackdown On Insecure IoT Devices

October 16, 2017 by Jenny List 36 Comments

We’ve all seen the stories about IoT devices with laughably poor security. Both within our community as fresh vulnerabilities are exposed and ridiculed, and more recently in the wider world as stories of easily compromised baby monitors have surfaced in mass media outlets. It’s a problem with its roots in IoT device manufacturers treating their products as appliances rather than software, and in a drive to produce them at the lowest possible price.

The Australian government have announced that IoT security is now firmly in their sights, announcing a possible certification scheme with a logo that manufacturers would be able to use if their products meet a set of requirements. Such basic security features as changeable, non-guessable, and non-default passwords are being mentioned, though we’re guessing that would also include a requirement not to expose ports to the wider Internet. Most importantly it is said to include a requirement for software updates to fix known vulnerabilities. It is reported that they are also in talks with other countries to harmonize some of these standards internationally.

It is difficult to see how any government could enforce such a scheme by technical means such as disallowing Internet connection to non-compliant devices, and if that was what was being proposed it would certainly cause us some significant worry. Therefore it’s likely that this will be a consumer certification scheme similar to for example the safety standards for toys, administered as devices are imported and through enforcement of trading standards legislation. The tone in which it’s being sold to the public is one of “Think of the children” in terms of compromised baby monitors, but as long-time followers of Hackaday will know, that’s only a small part of the wider problem.

Thanks [Bill Smith] for the tip.

Baby monitor picture: Binatoneglobal [CC BY-SA 3.0].

Inside Two-Factor Authentication Apps

October 16, 2017 by Elliot Williams 66 Comments

Passwords are in a pretty broken state of implementation for authentication. People pick horrible passwords and use the same password all over the place, firms fail to store them correctly and then their databases get leaked, and if anyone’s looking over your shoulder as you type it in (literally or metaphorically), you’re hosed. We’re told that two-factor authentication (2FA) is here to the rescue.

Well maybe. 2FA that actually implements a second factor is fantastic, but Google Authenticator, Facebook Code Generator, and any of the other app-based “second factors” are really just a second password. And worse, that second password cannot be stored hashed in the server’s database, which means that when the database is eventually compromised, your “second factor” blows away with the breeze.

Second factor apps can improve your overall security if you’re already following good password practices. We’ll demonstrate why and how below, but the punchline is that the most popular 2FA app implementations protect you against eavesdropping by creating a different, unpredictable, but verifiable, password every 30 seconds. This means that if someone overhears your login right now, they wouldn’t be able to use the same login info later on. What 2FA apps don’t protect you against, however, are database leaks.

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Oh Great, WPA2 Is Broken

October 16, 2017 by Brian Benchoff 131 Comments

WPA2, the standard security for Wi-Fi networks these days, has been cracked due to a flaw in the protocol. Implications stemming from this crack range from decrypting Wi-Fi, hijacking connections, and injecting content. It’s fair to say, WPA2 is now Considered Harmful. The paper is available here (PDF).

This is a proof-of-concept exploit, and like all headline-making network security stories, it has a name. It’s called KRACK, for Key Reinstallation Attack. The key insight to this exploit is a vulnerability in the handshaking between routers and devices to establish a secure connection.

This is not the first time the researchers behind this exploit have found holes in WPA2. In a paper published by the KRACK researchers at the USENIX Symposium last August (PDF), they showed that the Random Number Generator used in 802.11 is flawed, ill-defined, and insecure. The researchers have also spoken at 33c3 on predicting WPA2 Group Keys.

The practical consequences of a poor definition and implementation of an RNG can be found in consumer hardware. The researchers found that in MediaTek-based routers, the only source of randomness is the current time. Meanwhile Broadcom-based routers do not use the RNG proposed by the 802.11 spec, but instead take the MD5 of the current time in microseconds. The researchers do not mention if the current time is a secret.

So what do we do now?

This has happened before. In 2001, WEP, the Wi-Fi security protocol many security-ignorant people are still running, was cracked in much the same was as KRACK. This quickly led to the development of Aircrack, and in 2003, the Wi-Fi Alliance rolled out WPA and WPA2. Sure, you can still select a deprecated security protocol for your router, but the problem of WEP hacking is as solved as it’s ever going to be.

The early 2000s were a different time when it came to wireless networks, though here in 2017 Wi-Fi permeates every cubic inch of our lives. Everything and everyone has Wi-Fi now. This is going to be a bit bigger than cracking WEP, but it remains possible to patch devices to ensure that this exploit is rendered useless. Install those security updates, people! Of course there will still be millions of unpatched devices in a year’s time, and for those routers, IoT baubles, and other wireless devices, turning on WPA2 will be akin to having no security at all.

That said, this isn’t a world-ending Armageddon in the way the botnet of webcams was. You will only be vulnerable if an attacker is within range of your router, and you will still be secure if you’re accessing secure websites. However, turning off Wi-Fi on your phone, relying on mobile data, not ignoring HTTPS cert warnings, and plugging into an Ethernet port might not be a bad idea.

Encryption For The Most Meager Of Devices

October 15, 2017 by Jenny List 57 Comments

It seems that new stories of insecure-by-design IoT devices surface weekly, as the uneasy boundary is explored between the appliance and the Internet-connected computer. Manufacturers like shifting physical items rather than software patches, and firmware developers may not always be from the frontline of Internet security.

An interesting aside on the security of IoT traffic comes from [boz], who has taken a look at encryption of very low data rate streams from underpowered devices. Imagine perhaps that you have an Internet-connected sensor which supplies only a few readings a day that you would like to keep private. Given that your sensor has to run on tiny power resources so a super-powerful processor is out of the question, how do you secure your data? Simple encryption schemes are too easily broken.

He makes the argument for encryption from a rather unexpected source: a one-time pad. We imagine a one-time pad as a book with pages of numbers, perhaps as used by spies in Cold-War-era East Berlin or something. Surely storing one of those would be a major undertaking! In fact a one-time pad is simply a sequence of random keys that are stepped through, one per message, and if your message is only relatively few bytes a day then you have no need to generate more than a few K of pad data to securely encrypt it for years. Given that even pretty meager modern microcontrollers have significant amounts of flash at their disposal, pad storage for sensor data of this type is no longer a hurdle.

Where some controversy might creep in is the suggestion that a pad could be recycled when its last entry has been used. You don’t have to be a cryptologist to know that reusing a one-time pad weakens the integrity of the cypher, but he has a valid answer there too, If the repeat cycle is five years, your opponent must have serious dedication to capture all packets, and at that point it’s worth asking yourself just how sensitive the sensor data in question really is.

Encrypt Data On The Fly On A Pi With Cryptopuck

October 13, 2017 by Tom Nardi 22 Comments

There was a time that encryption was almost a dirty word; a concept that really only applied to people with something to hide. If you said you wanted to encrypt your hard drive, it may as well have been an admission to a crime. But now more than ever it’s clear that encryption, whether it’s on our personal devices or on the web, is a basic necessity in a digital society. The age of Big Data is upon us, and unless you’re particularly fond of being a row in a database, you need to do everything you can to limit the amount of plaintext data you have.

Of course, it’s sometimes easier said than done. Not everyone has the time or desire to learn how the different cryptographic packages work, others may be working on systems that simply don’t have the capability. What do you do when you want to encrypt some files, but the traditional methods are out of reach?

Enter the latest project from [Dimitris Platis]: Cryptopuck. By combining the ever-versatile Raspberry Pi Zero, some clever Python programs, and a few odds and ends in a 3D printed case, he has created a completely self-contained encryption device that anyone can use. Stick a USB flash drive in, wait for the LED to stop blinking, and all your files are now securely encrypted and only accessible by those who have the private key. [Dimitris] envisions a device like this could be invaluable for reporters and photographers on the front lines, protesters, or really anyone who needs a discreet way of quickly securing data but may not have access to a computer.

The hardware side is really just the Pi, a switch, a single LED for notifications, and a battery. The real magic comes from the software, where [Dimitris] has leveraged PyCrypto to perform the AES-256 encryption, and a combination of pyinotify and udiskie to detect new mounted volumes and act on them. The various Python scripts that make up the Cryptopuck suite are all available on the project’s GitHub page, but [Dimitris] makes it very clear the software is to be considered a proof of concept, and has not undergone any sort of security audit.

For some background information on how the software used by the Cryptopuck works you may want to check out this excellent primer from a few years back; though if you’d like to read up on why encryption is so important, you don’t need to go nearly as far back in time.

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