Tag Archives: Elliptic Curve Cryptography

Security coprocessor marks a new approach to provisioning for IoT edge devices

A New Approach to Provisioning

It’s worth noting that security breaches rarely involve breaking the encryption code; hackers mostly use techniques like spoofing to steal the ID. So, the focus of the ATECC508A crypto engine is the tasks such as key generation and authentication. The chip employs ECC math to ensure sign-verify authentication and subsequently the verification of the key agreement.

The IoT security — which includes the exchange of certificates and other trusted objects — is implemented at the edge node in two steps: provisioning and commissioning. Provisioning is the process of loading a unique private key and other certificates to provide identity to a device while commissioning allows the pre-provisioned device to join a network. Moreover, provisioning is carried out during the manufacturing or testing of a device and commissioning is performed later by the network service provider and end-user.

Presently, snooping threats are mostly countered through hardware security module (HSM), a mechanism to store, protect and manage keys, which requires a centralized database approach and entails significant upfront costs in infrastructure and logistics. On the other hand, the ATECC508A security coprocessor simplifies the deployment of secure IoT nodes through pre-provisioning with internally generated unique keys, associated certificates and certification-ready authentication.

It’s a new approach toward provisioning that not only prevents over-building, as done by the HSM-centric techniques, but also prevents cloning for the gray market. The key is controlled by a separate chip, like the ATECC508A coprocessor. Meaning, if there are 1,000 IoT systems to be built, there will be exactly 1,000 security coprocessors for them.

Certified-ID Security Platform

Back at ARM TechCon 2015, Atmel went one step ahead when it announced the availability of Certified-ID security platform for the IoT entry points like edge devices to acquire certified and trusted identities. This platform leverages internal key generation capabilities of the ATECC508A security coprocessor to deliver distributed key provisioning for any device joining the IoT network. That way it enables a decentralized secure key generation and eliminates the upfront cost of building the provisioning infrastructure for IoT setups being deployed at smaller scales.

Atmel, a pioneer in Trusted Platform Module (TPM)-based secure microcontrollers, is now working with cloud service providers like Proximetry and Exosite to turn its ATECC508A coprocessor-based Certified-ID platform into an IoT edge node-to-cloud turnkey security solution. TPM chips, which have roots in the computer industry, aren’t well-positioned to meet the cost demands of low-price IoT edge devices.

Additionally, the company has announced the availability of two provisioning toolkits for low volume IoT systems. The AT88CKECCROOT toolkit is a ‘master template’ that creates and manages certificate root of trust in any IoT ecosystem. On the other hand, AT88CKECCSIGNER is a production kit that allows designers and manufacturers to generate tamper-resistant keys and security certifications in their IoT applications.

Atmel launches next-generation CryptoAuthentication device

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Atmel becomes first to ship ultra-secure crypto element enabling smart, connected and secure systems.

Just announced, the Atmel ATECC508A is the first device to integrate ECDH (Elliptic Curve Diffie–Hellman) security protocol — an ultra-secure method to provide key agreement for encryption/decryption, along with ECDSA (Elliptic Curve Digital Signature Algorithm) sign-verify authentication — for the Internet of Things (IoT) market including home automation, industrial networking, accessory and consumable authentication, medical and mobile, among many others.

Atmel’s ATECC508A is the second integrated circuit (IC) in the CryptoAuthentication portfolio with advanced Elliptic Curve Cryptography (ECC) capabilities. With built-in ECDH and ECDSA, this device is ideal for the rapidly growing IoT market by easily providing confidentiality, data integrity and authentication in systems with MCU or MPUs running encryption/decryption algorithms (such as AES) in software. Similar to all Atmel CryptoAuthentication products, the new ATECC508A employs ultra-secure hardware-based cryptographic key storage and cryptographic countermeasures which are more secure than software-based key storage.

This next-generation CryptoAuthentication device is compatible with any microcontroller or microprocessor on the market today including Atmel | SMART and Atmel AVR MCUs and MPUs. As with all CryptoAuthentication devices, the ATECC508A delivers extremely low-power consumption, requires only a single general purpose I/O over a wide voltage range, and available in a tiny form factor, making it ideal for a variety of applications that require longer battery life and flexible form factors.

“As a leader in security, Atmel is committed to delivering innovative secure solutions to the billions of devices to be connected in the IoT market,” explained Rob Valiton, SVP and GM of Atmel’s Automotive, Aerospace and Memory Business Units. “Atmel’s newest CryptoAuthentication IC is the first of its kind to apply hardware-based key storage to provide the full complement of security capabilities, specifically confidentiality, data integrity and authentication. We are excited to continue bringing ultra-secure crypto element solutions to a wide range of applications including IoT, wireless, consumer, medical, industrial, and automotive, among others.”

Key security features of the ATECC508A include:

Optimized key storage and authentication
ECDH operation using stored private key
ECDSA (elliptic-curve digital signature algorithm) sign-verify
Support for X.509 certificate formats
256-bit SHA/HMAC hardware engine
Multilevel RNG using FIPS SP 800-90A DRBG
Guaranteed 72-bit unique ID
I2C and single-wire interfaces
2 to 5.5V operation, 150-nA standby current
10.5-kbit EEPROM for secret and private keys
High-Endurance Monotonic Counters
UDFN, SOIC, and 3-lead contact packages

In the wake of recent incidents, it is becoming increasingly clear that embedded system insecurity impacts everyone and every company. The effects of insecurity may not only be personal, such as theft of sensitive financial and medical data, but a bit more profound on the corporate level. Products can be cloned, software copied, systems tampered with and spied on, and many other things that can lead to revenue loss, increased liability, and diminished brand equity.

Data security is directly linked to how exposed the cryptographic key is to being accessed by unintended parties including hackers and cyber-criminals. The best solution to keeping the “secret key secret” is to lock it in protected hardware devices. That is exactly what this latest iteration of security devices have, are and will continue to do. They are an inexpensive, easy, and ultra-secure way to protect firmware, software, and hardware products from cloning, counterfeiting, hacking, and other malicious threats.

Interested in learning more? Discover the latest in hardware-based security here. Meanwhile, you may also want to browse through recent articles on the topic, including “Is the Internet of Things just a toy?,” “Greetings from Digitopia,” “What’s ahead this year for digital insecurity?,” and “Don’t be an ID-IoT.”

Symmetric or asymmetric encryption, that is the question!

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With the emergence of breaches and vulnerabilities, the need for hardware security has never been so paramount.

Confidentiality — one of the three foundational pillars of security, along with data integrity and authenticity — is created in a digital system via encryption and decryption. Encryption, of course, is scrambling a message in a certain way that only the intended party can descramble (i.e. decrypt) it and read it.

Throughout time, there have been a number of ways to encrypt and decrypt messages. Encryption was, in fact, used extensively by Julius Caesar, which led to the classic type of encryption aptly named, Caesar Cipher. The ancient Greeks beat Caesar to the punch, however. They used a device called a “Scytale,” which was a ribbon of leather or parchment that was wrapped around a rod of a diameter, of which only the sender and receiver were aware. The message was written on the wrapping and unfurled, then sent to the receiver who wrapped on on the rod of the same diameter in order to read it.

Modern Encryption

Modern encryption is based on published and vetted digital algorithms, such as Advanced Encryption System (AES), Secure Hashing Algorithms (SHA) and Elliptic Curve Cryptography (ECC), among many others. Given that these algorithms are public and known to everyone, the security must come from something else — that thing is a secret cryptographic “key.” This fundamental principal was articulated in the 19th century by Auguste Kerckhoffs, a Dutch linguist, cryptographer and professor.

Kerckhoffs’ principle states that a cryptosystem should be secure even if everything about the system, except the key, is public knowledge. In other words: “The key to encryption is the key.” Note that Kirchoffs advocated what is now commonly referred to as “open-source” for the algorithm. Point being, this open-source method is more secure than trying to keep an algorithm itself obscured (sometimes called security by obscurity). Because the algorithms are known, managing the secret keys becomes the most important task of a cryptographer. Now, let’s look at that.

Symmetric and Asymmetric

Managing the key during the encryption-decryption process can be done in two basic ways: symm etric and asymmetric. Symmetric encryption uses the identical key to both encrypt and decrypt the data. Symmetric key algorithms are much faster computationally than asymmetric algorithms because the encryption process is less complicated. That’s because there is less processing involved.

The length of the key size directly determines the strength of the security. The longer the key, the more computation it will take to crack the code given a particular algorithm. The table below highlights the NIST guidelines for key length for different algorithms with equivalent security levels. You can see that Elliptic Curve Cryptography (ECC) is a very compact algorithm. It has a small software footprint, low hardware implementation costs, low bandwidth requirements, and high device performance. That is one of the main reasons that ECC-based asymmetric cryptographic processes, such as ECDSA and ECDH, are now being widely adopted. The strength of the sophisticated mathematics of ECC are a great ally of all three pillars of security, especially encryption.

Not only is symmetric faster and simpler; furthermore, a shorter key length can be used since the keys are never made public as is the case with asymmetric (i.e. Public Key Infrastructure) encryption. The challenge, of course, with symmetric is that the keys must be kept secret on both the sender and receiver sides. So, distributing a shared key to both sides is a major security risk. Mechanisms that maintain the secrecy of the shared key are paramount. One method for doing this is called Symmetric Session Key Exchange.

Asymmetric encryption is different in that it uses two mathematically related keys (a public and private key pair) for data encryption and decryption. That takes away the security risk of key sharing. However, asymmetric requires much more processing power. Unlike the public key, the private key is never exposed. A message that is encrypted by using a public key can only be decrypted by applying the same algorithm and using the matching private key.

A message that is encrypted by using the private key can only be decrypted by using the matching public key. This is sort of like mathematical magic. Some of the trade offs of symmetric and asymmetric are summarized below.

Symmetric

Keys must be distributed in secret
If a key is compromised the attacker can decrypt any message and/or impersonate one of the parties
A network requires a large number of keys

Asymmetric

Around 1000 times slower than symmetric
Vulnerability to a “man-in-the-middle” attack, where the public key is intercepted and altered

Due to the time length associated with asymmetric, many real-world systems utilize combination of the two, where the secret key used in the symmetric encryption is itself encrypted with asymmetric encryption, and sent over an insecure channel.Then, the rest of the data is encrypted using symmetric encryption and sent over the insecure channel in the encrypted format. The receiver gets the asymmetrically encrypted key and decrypts it with his private key. Once the receiver has the symmetric key, it can be used to decrypt the symmetrically encrypted message. This is a type of key exchange.

Note that the man in the middle vulnerability can be easily addressed by employing the other pillar of security; namely authentication. Crypto engine devices with hardware key storage, most notably Atmel’s CrypotoAuthentication, have been designed specifically to address all three pillars of security in an easy to design and cost-effective manner. Ready to secure your next design? Get started here.

Atmel and IoT and Crypto, oh my!

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One of the companies that is best positioned to supply components into the Internet of Things (IoT) market is Atmel. For the time being most designs will be done using standard components, not doing massive integration on an SoC targeted at a specific market. The biggest issue in the early stage of market development will be working out what the customer wants and so the big premium will be on getting to market early and iterating fast, not premature cost optimization for a market that might not be big enough to support the design/NRE of a custom design.

Latest product in Atmel's SmartConnect family, the SAM W25 module

Here is Atmel’s latest product in the SmartConnect family, the SAM W25 module

Atmel has microcontrollers, literally over 500 different flavors and in two families, the AVR family and a broad selection of ARM microcontrollers ad processors. They have wireless connectivity. They have strong solutions in security.

Indeed last week at Electronica in Germany they announced the latest product in the SmartConnect family, the SAM W25 module. It is the industry’s first fully-integrated FCC-certified Wi-Fi module with a standalone MCU and hardware security from a single source. The module is tiny, not much larger than a penny. The module includes Atmel’s recently-announced 2.4GHz IEEE 802.11 b/g/n Wi-Fi WINC1500, along with an Atmel | SMART SAM D21 ARM Cortex M0+-based MCU and Atmel’s ATECC108A optimized CryptoAuthentication engine with ultra-secure hardware-based key storage for secure connectivity.

Atmel at Electronica 2014

That last item is a key component for many IoT designs. Security is going to be a big thing and with so many well-publicized breaches of software security, the algorithms, and particularly the keys, are moving quickly into hardware. That component, the ATECC108A, provides state-of-the-art hardware security including a full turnkey Elliptic Curve Digital Signature Algorithm (ECDSA) engine using key sizes of 256 or 283 bits – appropriate for modern security environments without the long computation delay typical of software solutions. Access to the device is through a standard I²C Interface at speeds up to 1Mb/sec. It is compatible with standard Serial EEPROM I²C Interface specifications. Compared to software, the device is:

Higher performance (faster encryption)
Lower power
Much harder to compromise

Atmel has a new white paper out, Integrating the Internet of Things, Necessary Building Blocks for Broad Market Adoption. Depending on whose numbers you believe, there will be 50 billion IoT edge devices connected by 2020.

Edge nodes are becoming integrated into everyone’s life

As it says in the white paper:

On first inspection, the requirements of an IoT edge device appear to be much the same as any other microcontroller (MCU) based development project. You have one or more sensors that are read by an MCU, the data may then be processed locally prior to sending it off to another application or causing another event to occur such as turning on a motor. However, there are decisions to be made regarding how to communicate with these other applications. Wired, wireless, and power line communication (PLC) are the usual options. But, then you have to consider that many IoT devices are going to be battery powered, which means that their power consumption needs to be kept as low as possible to prolong battery life. The complexities deepen when you consider the security implications of a connected device as well. And that’s not just security of data being transferred, but also ensuring your device can’t be cloned and that it does not allow unauthorized applications to run on it.

IoT design requirements: Software / development tools ecosystem

For almost any application, the building blocks for an IoT edge node are the same:

Embedded processing
Sensors
Connectivity
Security
And while not really a “building block,” ultra-low power for always-on applications

My view is that the biggest of these issues will be security. After all, even though Atmel has hundreds of different microcontrollers and microprocessors, there are plenty of other suppliers. Same goes for connectivity solutions. But strong cryptographhic solutions implemented in hardware are much less common.

The new IoT white paper is available for download here.

This post has been republished with permission from SemiWiki.com, where Paul McLellan is a featured blogger. It first appeared there on November 19, 2014.

Don’t be an “ID-IoT”

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Authentication may just be the “sine qua non” of the Internet of Things.

Let’s just come out and say it: Not using the most robust security to protect your digital ID, passwords, secret keys and other important items is a really, really bad idea. That is particularly true with the coming explosion of the Internet of Things (IoT).

The identity (i.e. “ID”) of an IoT node must be authenticated and trusted if the IoT is ever to become widely adopted. Simply stated, the IoT without authenticated ID is just not smart. This is what we mean when we say don’t be an ID-IoT.

It seems that every day new and increasingly dangerous viruses are infecting digital systems. Viruses — such as Heartbleed, Shellshock, Poodle, and Bad USB — have put innocent people at risk in 2014 and beyond. A perfect case in point is that Russian Cyber gangs (a.k.a. “CyberVor”) have exposed over a billion user passwords and IDs — so far. What’s scary is that the attacks are targeted at the very security mechanisms that are meant to provide protection.

If you think about it, that is somewhat analogous to how the HIV/AIDS virus attacks the very immune system that is supposed to protect the host organism. Because the digital protection mechanisms themselves have become targets, they must be hardened. This has become increasingly important now that the digital universe is going through its own Big Bang with the explosion of the IoT. This trend of constant connectivity will result in billions of little sensing and communicating processors being distributed over the earth, like dust. According to Gartner, processing, communicating and sensing semiconductors (which comprise the IoT) will grow at a rate of over 36% in 2015, dwarfing the overall semiconductor market growth of 5.7%. Big Bang. Big growth. Big opportunity.

The IoT will multiply the number of points for infection that hackers can attack by many orders of magnitude. It is not hard to see that trust in the data communicated via an ubiquitous (and nosey) IoT will be necessary for it to be widely adopted. Without trust, the IoT will fail to launch. It’s as simple as that. In fact, the recognized inventor of the Internet, Vint Cerf, completely agrees saying that the Internet of Things requires strong authentication. In other words, no security? No IoT for you!

There is much more to the story behind why the IoT needs strong security. Because the world has become hyper-connected, financial and other sensitive transactions have become almost exclusively electronic. For example, physical checks don’t need to be collected and cancelled any more — just a scanned electronic picture does the job. Indeed, the September 11th terror attacks on the U.S. that froze air travel and the delivery of paper checks accelerated the move to using images to clear checks to keep the economy moving.

Money now is simply electronic data, so everyone and every company are at risk of financial losses stemming directly from data breaches. See? Data banks are where the money is now kept, so data is what criminals attack. While breaches are, in fact, being publicized, there has not been much open talk about their leading to significant corporate financial liability. That liability, however, is real and growing. CEOs should not be the least bit surprised when they start to be challenged by significant shareholder and class action lawsuits stemming from security breaches.

Although inadvertent, companies are exposing identities and sensitive financial information of millions of customers, and unfortunately, may not be taking all the necessary measures to ensure the security and safety of their products, data, and systems. Both exposure of personal data and risk of product cloning can translate to financial damages. Damages translate to legal action.

The logic of tort and securities lawyers is that if proven methods to secure against hacking and cloning already exist, then it is the fiduciary duty of the leaders of corporations (i.e. the C-suite occupants) to embrace such protection mechanisms (like hardware-based key storage), and more importantly, not doing so could possibly be argued as being negligent. Agree or not, that line of argumentation is viable, logical, and likely.

A few CEOs have already started to equip their systems and products with strong hardware-based security devices… but they are doing it quietly and not telling their competitors. This also gives them a competitive edge, besides protecting against litigation.

Software, Hardware, and Hackers

Why is it that hackers are able to penetrate systems and steal passwords, digital IDs, intellectual property, financial data, and other secrets? It’s because until now, only software has been used to protect software from hackers. Hackers love software. It is where they live.

The problem is that rogue software can see into system memory, so it is not a great place to store important things such as passwords, digital IDs, security keys, and other valuable things. The bottom line is that all software is vulnerable because software has bugs despite the best efforts of developers to eliminate them. So, what about storing important things in hardware?

Hardware is better, but standard integrated circuits can be physically probed to read what is on the circuit. Also, power analysis can quickly extract secrets from hardware. Fortunately, there is something that can be done.

Several generations of hardware key storage devices have already been deployed to protect keys with physical barriers and cryptographic countermeasures that ward off even the most aggressive attacks. Once keys are securely locked away in protected hardware, attackers cannot see them and they cannot attack what they cannot see. Secure hardware key storage devices — most notably Atmel CryptoAuthentication — employ both cryptographic algorithms and a tamper-hardened hardware boundary to keep attackers from getting at the cryptographic keys and other sensitive data.

The basic idea behind such protection is that cryptographic security depends on how securely the cryptographic keys are stored. But, of course it is of no use if the keys are simply locked away. There needs to be a mechanism to use the keys without exposing them — that is the other part of the CryptoAuthentication equation, namely crypto engines that run cryptographic processes and algorithms. A simple way to access the secret key without exposing it is by using challenges (usually random numbers), secret keys, and cryptographic algorithms to create unique and irreversible signatures that provide security without anyone being able to see the protected secret key.

Crypto engines make running complex mathematical functions easy while at the same time keeping secret keys secret inside robust, protected hardware. The hardware key storage + crypto engine combination is the formula to keeping secrets, while being easy-to-use, available, ultra-secure, tiny, and inexpensive.

While the engineering that goes into hardware-based security is sophisticated, Atmel does all the crypto engineering so there is no need to become a crypto expert. Get started by entering for your chance to take home a free CryptoAuthentication development tool.

ECDH key exchange is practical magic

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What if you and I want to exchange encrypted messages? It seems like something that will increasingly be desired given all the NSA/Snowden revelations and all the other snooping shenanigans. The joke going around is that the motto of the NSA is really “Yes We Scan,” which sort of sums it up.

Encryption is essentially scrambling a message so only the intended reader can see it after they unscramble it. By definition, scrambling and unscrambling are inverse (i.e. reversible) processes. Doing and undoing mathematical operations in a secret way that outside parties cannot understand or see is the basis of encryption/decryption.

Julius Caesar used encryption to communicate privately. The act of shifting the alphabet by a specific number of places is still called the Caesar cipher. Note that the number of places is kept secret and acts as the key. Before Caesar, the Spartans used a rod of a certain thickness that was wrapped with leather and written upon with the spaces not part of the message being filled with decoy letters so only someone with the right diameter rod could read the message. This was called a skytale. The rod thickness acts as the key.

A modern-day encryption key is a number that is used by an encryption algorithm, such as AES (Advanced Encryption Standard) and others, to encode a message so no one other than the intended reader can see it. Only the intended parties are supposed to have the secret key. The interaction between a key and the algorithm is of fundamental importance in cryptography of all types. That interaction is where the magic happens. An algorithm is simply the formula that tells the processor the exact, step-by-step mathematical functions to perform and the order of those functions. The algorithm is where the magical mathematical spells are kept, but those are not kept secret in modern practice. The key is used with the algorithm to create secrecy.

For example, the magic formula of the AES algorithm is a substitution-permutation network process, meaning that AES uses a series of mathematical operations done upon the message to be encrypted and the cryptographic key (crypto people call the unencrypted message “plaintext“). How that works is that the output of one round of calculations done on the plaintext is substituted by another block of bits and then the output of that is changed (i.e. permutated) by another block of bits and then it happens over and over, again and again. This round-after-round of operations changes the coded text in a very confused manor, which is the whole idea. Decryption is exactly as it sounds, simply reversing the entire process.

That description, although in actual fact very cursory, is probably TMI here, but the point is that highly sophisticated mathematical cryptographic algorithms that have been tested and proven to be difficult to attack are available to everyone. If a secret key is kept secret, the message processed with that algorithm will be secret from unintended parties. This is called Kerckhoffs’ principle and is worth remembering since it is the heart of modern cryptography. What it says is that you need both the mathematical magic and secret keys for strong cryptography.

Another way to look at is that the enemy can know the formula, but it does him or her no good unless they know the secret key. That is, by the way, why it is so darn important to keep the secret key secret. Getting the key is what many attackers try to do by using a wide variety of innovative attacks that typically take advantage of software bugs. So, the best way to keep the secret is to store the key in secure hardware that can protect if from attacks. Software storage of keys is just not as strong as hardware storage. Bugs are endemic, no matter how hard the coders try to eliminate them. Hardware key storage trumping software is another fundamental point worth remembering.

Alright, so now that we have a good algorithm (e.g. AES) and a secret key we can start encrypting and feel confident that we will obtain confidentiality.

Key Agreement

In order for encryption on the sender’s side and decryption on the receiver’s side, both sides must agree to have the same key. That agreement can happen in advance, but that is not practical in many situations. As a result, there needs to be a way to exchange the key during the session where the encrypted message is to be sent. Another powerful cryptographic algorithm will be used to do just that.

There is a process called ECDH key agreement, which is a way to send the secret key without either of the sides actually having to meet each other. ECDH uses a different type of algorithm from AES that is called “EC” to send the secret key from one side to the other. EC stands for elliptic curve, which literally refers to a curve described by an elliptic equation. A certain set of elliptic curves (defined by the constants in the equation) have the property that given two points on the curve (P and Q) there is a third point, P+Q, on the curve that displays the properties of commutivity, associativity, identity, and inverses when applying elliptic curve point multiplication. Point-multiplication is the operation of successively adding a point along an elliptic curve to itself repeatedly. Just for fun the shape of such an elliptic curve is shown in the diagram.

The thing that makes this all work is that EC point-multiplication is doable, but the inverse operation is not doable. Cryptographers call this a one-way or trap door function. (Trap doors go only one way, see?) In regular math, with simple algebra if you know the values of A and A times B you can find the value of B very easily. With Elliptic curve point-multiply if you know A and A point-multiplied by B you cannot figure out what B is. That is the magic. That irreversibility and the fact that A point-multiplied by B is equal to B point-multiplied by A (i.e. commutative) are what makes this a superb encryption algorithm, especially for use in key exchange.

To best explain key agreement with ECDH, let’s say that everyone agrees in advance on a number called G. Now we will do some point-multiply math. Let’s call the sender’s private key PrivKeySend. (Note that each party can be a sender or receiver, but for this purpose we will name one the sender and the other the receiver just to be different from using the typical Alice and Bob nomenclature used by most crpyto books.) Each private key has a mathematically related and unique public key that is calculated using the elliptic curve equation. Uniqueness is another reason why elliptic curves are used. If we point-multiply the number G by PrivKeySend we get PubKeySend. Let’s do the same thing for the receiver who has a different private key called PrivKeyReceive and point-multiply that private key by the same number G to get the receiver’s public key called PubKeyReceive. The sender and receiver can then exchange their public keys with each other on any network since the public keys do not need to be kept secret. Even an unsecured email is fine.

Now, the sender and receiver can make computations using their respective private keys (which they are securely hiding and will never share) and the public key from the other side. Here is where the commutative law of point-multiply will work its magic. The sender point-multiplies the public key from the other side by his or her stored private key. This is equates to:

PubKeyReceive point-multiplied by PrivKeySend which = G point-multiplied by PrivKeyReceive point-multiplied by PrivKeySend

The receiver does the same thing using his or her private key and the public key just received. This equates to:

PubKeySend point-multiplied by PrivKeyReceive = G point-multiplied by PrivKeySend point-multiplied by PrivKeyReceive.

Because point-multiply is commutative these equations have the same value!

And, the rabbit comes out of the hat: The sender and receiver now have the exact same value, which can now be used as the new encryption key for AES, in their possession. No one besides them can get it because they would need to have one of the private keys and they cannot get them. This calculated value can now be used by the AES algorithm to encrypt and decrypt messages. Pretty cool, isn’t it?

Below is a wonderful video explaining the modular mathematics and discrete logarithm problem that creates the one-way, trapdoor function used in Diffie-Hellman key exhange. (Oh yeah, the “DH” in ECDH stands for Diffie-Hellman who were two of the inventors of this process.)

Are you building out for secure devices? Protect your design investments and prevent compromise of your products? Receive a FREE Atmel CryptoAuthentication™ development tool.

The “Key” to Reality

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If we wanted to reduce the definition of authentication to its most Zen-like simplicity, we could say authentication is “keeping things real.” To keep something real you need to have some sort of confirmation of its identity, as confirmation is the key (so to speak).

The equation could be as follows:

Identification + Confirmation = Authentication

Confirming or validating the identity of a document, item, data, etc. is what keeping things real is all about. Some of the “things” that can be authenticated with cryptographic methods are mobile, medical, and consumer accessories; embedded firmware; industrial network nodes; and sensors, among others. Soon IoT and vehicle-to-vehicle communication will join in.

Authentication is far more important than many people realize, especially in our growing hyper-connected world that now links billions of people (and things). In cyber-land, authentication is accomplished by deploying cryptographic keys and algorithms. Keys are fundamental to keeping things real—so that is what we mean by “the key to reality.”

There are two primary types of Authentication: Symmetric and Asymmetric. Atmel offers secure key storage devices for both types. These two important techniques take their names directly from whether the keys on each side (i.e. the host and client sides) are the same or different.

Symmetric Authentication

If the same secret key is used on the client and on the host, then the application is symmetric, just like the name suggests. Both of the symmetric keys must be protected because if either one gets out then the security will be lost. This is perhaps analogous to having two sets of car keys. Meaning, losing either one makes it easy for a thief to drive away with your car. So, the secret keys must stay secret.

Symmetric Keys are the Same

The identical keys on the host and client are used in mathematical calculations to test the reality of client devices. A very common mathematical calculation that is used is a hash function based upon a cryptographic algorithm (such as SHA). A hash operation produces a hash value (also called “digest”), which is a number of a specified length that is usually smaller than the numbers used as the inputs. A hash is a one-way operation, which means that the inputs cannot be recreated from the hash value.

With symmetric authentication a typical process is to challenge the client device to be authenticated by sending it a random number. The client then puts the random number challenge and a secret key into the hash algorithm to create a hash value, which is known as the “response.” Each challenge will generate a unique response.

It should be noted that cryptographers call a hash of a random number with a secret key a “Message Authentication Code” or “MAC.” The diagram below illustrates this process. Because the host key is the same on the host and client sides, the exact same calculation can run on the host. Once that happens, the hash values (“MACs”) from each can be compared. If the hash values match, the client is considered to be real. You can see that symmetric authentication is really a simple process, but it is loaded with mathematical elegance. Now let’s look at asymmetric authentication.

Hashing a Random Number with a Secret Key

Asymmetric Authentication.

Asymmetric keys are presented in public-private pairs. More specifically, the public and private keys are related to each other via a mathematical algorithm. An example would be the Elliptic Curve Cryptography (or “ECC”) algorithm. Only the private key has to be securely stored. Because the keys are different, asymmetric authentication cannot use the same calculate-and-compare process as symmetric.

Asymmetric requires more complicated techniques such as making digital signatures that are verified for authenticity (this is called “Sign-Verify”). An example of asymmetric authentication using ECC algorithms is Elliptic Curve Digital Signature Algorithm (or “ECDSA”). A major benefit of the Atmel ATECC108A device is that it can be used to easily implement ECDSA sign-verify. (The steps of ECDSA are very interesting, but they will be covered in a separate article). Note that an important trade-off between symmetric and asymmetric authentication is the speed of operation. For example, authentication time for the Atmel ATSHA204A is 12ms (typical) for symmetric versus more than a second for many microcontrollers to execute an asymmetric ECDSA operation.

Getting back to the keys: The secret keys must stay secret. If keys are the keys to authentication (i.e. reality), then secure storage of the secret keys is the key to SECURE authentication. And that is the real point here.

So the, how is secure storage implemented? The best way is to use hardware key storage devices that can withstand attacks that try to read the key(s). Atmel CryptoAuthentication products such as the ATSHA204A, ATECC108A and ATAES132 implement hardware-based storage, which is much stronger than software based storage because of the defense mechanisms that only hardware can provide against attacks. Secure storage in hardware beats storage in software every time. Adding secure key storage is an inexpensive, easy, and ultra-secure way to protect firmware, software and hardware products from cloning, counterfeiting, hacking, as well as other malicious threats.

For more details on Atmel CryptoAuthentication products, please view the links above or the introduction page CryptoAuthentication. Future Bits & Pieces articles will take in an in-depth look at how symmetric and asymmetric authentication is accomplished.

What is authentication and why should you care?

ATECC108 deep dive: Part 2

A New Approach to Provisioning

Certified-ID Security Platform

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Modern Encryption

Symmetric and Asymmetric

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Software, Hardware, and Hackers

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Key Agreement

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