Nowadays with the development of technology and the fact that it has influenced every aspect of people's lives, the information is the most essential factor to be considered, since it is the fundamental in which technology is being built. On the contrary, cybersecurity attacks are growing rapidly year after year since everyone around the world is seriously involved in this wild race of having access to the information owned by the others. Data breaches are also growing since hackers and non-authorized parties are attacking organizations, companies and other institutions of high importance. As a result, more and more companies are considering solutions that not only will protect the information, but will also keep un-authorized parties away from having access to it. Encryption is considered one of the most classic ways to ensure that sensitive information is converted into secret codes that will hide the information from un-authorized access. But what's the point to encrypting the information, when the keys are not totally safe and are at risk of being exposed. Cryptographical keys should be stored, kept and managed carefully, since their exposure would disclose the sensitive data the same way it as not even encrypted. That is the reason why companies, organizations and institutions globally are using Hardware Security Modules as the solution to secure and protect their sensitive data and to provide functionality for their cyber security purposes, including authentication, authorization, data confidentiality and data integrity. This paper aims to give a brief analysis of what a HSM is, how it functions and how it helps the companies and organizations in the context of cybersecurity. Furthermore, it will provide information on types of HSMs, architecture, different options offered on the market and most common use cases inthe recent years.
While there are a lot of measures widely used to protect sensitive data and keep the un-authorized parties away from having access to certain information, encryption is one of the most used and well-known methods to hide data’s true meaning behind secret codes, in such a way that even if someone has access, he/she can’t understand the content without having the proper key to decrypt it. On the other hand, encryption has its own disadvantages because key management brings potential security vulnerability since hackers can steal encryption keys and with the stolen key it is quite easy to decrypt the information and have access to sensitive and supposedly “protected” data. Thus, in order to ensure the security, during the recent years it is being used a key protection solution based on the hardware component of an information system called HSM.
The Hardware Security Modules can be used in a
wide variety of platforms and information systems
environments, where cryptographic functionalities
are used to offer a wider spectrum of protection and
security. There are different types of HMSs, such as
stand-alone devices, plug-in cards or even Hardware
Security Modules that are built into other devices.
Recently, the HSMs are well-known for being used
in cloud infrastructure, web servers, card payment
systems, banking and similar fields where important
cryptographic operations such as key generation,
encryption, decryption, signature generation and
hash functions are combined with hardware
components to ensure better data protection [
During the recent years, when the development of
technology has entirely changed every aspect of
people’s lives, they are all being exposed to
hackers, who are more and more exploiting
vulnerabilities of people, companies or systems to
profit more. It is now a wild race not only to have
access to other’s personal data, but also to
sensitive or confidential information being
processed in the systems that are being used by
companies, hospitals and governmental
institutions. As a result, since cryptography is
always necessary when having something to
protect, like information or money, HSMs
combine additional hardware features, to ensure a
more secure background for critical information
and financial assets. Thus, considering that
cryptography is being used to protect secret data,
the most important components that should be
taken special care of are the encryption and
decryption keys used in the process, in order to be
kept secret from adversary and also to ensure
confidentiality, integrity and availability. On the
other hand, every time data or information
security is being discussed, it is said that physical
component are always more vulnerable when it
comes to attacks or exposure. In this perspective,
how safe is it for companies, banks or institutions
to use the Hardware Security Modules as a critical
component for the encryption key management?
In the context of banks or other financial
institutions that use the card payment method and
the HMSs architecture, physical protection has
always been one of the most important things to
be remembered, even though in this case attacks
via the software running the host computer of the
HSM are neither less dangerous nor serious.
Nowadays everyone that has access on a network
such as office or school workstation, accessing
the Internet as a personal commodity or being
part of a more modern computing environment,
has been
faced even with the system vulnerabilities. Some of
them are for example different applications with
flawed interfaces, operating systems where
protection is not at the best state, security policies
that are often hard to be implemented and users as
the weakest part, can easily cause the biggest
problems from flawed authentication, absence of
knowledge or bad intentions. As a result, even
though it is harder to access an encapsulated circuit
board (HSM) from the network side, network
interface can be as weak as the physical one.
Moreover, HSMs are not only used to protect the
information from un-authorized individuals, but can
also be used to protect against problematic sites, for
example, a company can store on an HSM not just
SSL private keys but the entire server end of a Web
application, thus protecting its customers
information too [
HSMs ensure security and protection of sensitive data in all three states of the information:
Data-in-transit
The secure transmission of data-in-transit relies on
both encryption and authentication. Encryption does
not make data secure, but not using encryption,
however, means that any data-in-transit is totally easy
to be read [
Data-at-rest
This is also considered as storage encryption. It
protects data while it resides on the media/ device and
it involves encrypting data that will be decrypted
when it flows through the same point in the opposite
direction [
Data-in-use
HSM ensure security of data-in-use predominantly by
TEE, Trusted Execution Environment which is
commonly known as an isolated processing
environment in which applications can be securely
executed irrespective of the rest of the system [
Applying cryptographical operations in the real
word systems requires some specifications and one
of the most important factors is randomness.
Processes like key generation and management,
algorithms, encryption of information need
unpredictable randomness even by a lot of efforts.
As a result, this can be quite challenging and
difficult to be performed on a standard computer or
computing environment. Many types of
cryptographical algorithms such as RSA, DSA, and
Diffie-Hellman can be difficult for a standard CPU,
since at the same time, this machine should also
handle Web requests, update information, manage
network packets, organize interactive user responses
and so on. Thus, these processes are really
timeconsuming and the machine has to do them in
cycles and still manage to be performant [
From the Public-key cryptography context, basic
RSA encryption usually requires an algorithm
carefully designed to avoid cryptographic
weaknesses. Signature verification for example
requires performing cryptographic hashes and
because of such processes and operations, an
HSM’s cryptographic performance can incur an
unexpected dependence on the internal CPU,
especially if the HSM is matched with a too-slow
CPU [
As it was mentioned above, one of the most
important factors required for the HSMs to
function properly is randomness. Furthermore, for
ensuring correct cryptographical operations, the
seed used should be expanded into a longer
sequence that has to be random and undiscoverable
from any adversary [
Random number sequences are the fundamental for
many cryptographic algorithm and applications,
especially for the generation of strong and secure
keys that cannot be discovered by hackers or other
attackers. This is the reason why it is important for
the generated random numbers to be unpredictable.
There are different types of statistical tests that can
be applied to a sequence to evaluate the fact that the
sequence is truly random. To check the randomness
of sequences many different indexes are suggested.
Each index emphasizes only one part of the
phenomenon and measures its different aspects, for
example, the distribution of elements in the
sequence, dependencies between contiguous
reactions, counting tendencies, etc. They are
classified as Miyake et. al., 2000; Friedman &
Miyake, 2004; Towse & Neil, 1998. The first checks
equality of distribution of different possibilities, the
second checks indexes concerning relationships
between consecutive responses and the third
concerns repetitions of the same options in different
distances [
In the context of random number sequences there are
two main sources to generate them. TRNGs are
systems which extract randomness from
nonalgorithmic random phenomena, like temperature
fluctuations, radioactive decay, ambient radio noise,
hard disk access times, or user interactions with the
PC. Since the phenomena used are unpredictable,
TRNGs produce real random data instead of just
random periodic sequences [
Random number sequences need entropy and the main source how it is caused is from a noise source. Noise sources are divided into two categories, physical and non-physical sources. Physical noise sources use dedicated hardware to generate randomness; whereas non-physical noise sources use system data or human interaction input to generate randomness. As system data is used for example the output of API functions or data derived from RAM, while human inputs include for example keyboard strokes or mouse movements that are caused by the interaction with the machine.
Since physical noise sources are considered to
offer greater randomness, they are used in HSMs
in order to ensure more secure cryptographical
processes. Moreover, it is easier to find physical
noise sources in the environment. These sources
include physical phenomena such as thermal noise,
atmospheric noise, radioactive decay, keyboard
strokes or coin tossing. Noise sources are divided
in two classes:
Quantum-based noises
Non-quantum-based noises
Noise sources based on quantum effects are very
complex in implementation, but give stable results,
while non-quantum sources are more economical,
yet give unstable results. The quality of them
depends on various factors such as temperature
[
In cryptography and data encryption, the algorithm used in the process is public and anyone can have direct access to it. On the contrary, the difficult part and the factor which ensures the security is the key being used. It is the most essential part since it is also being used again in the decryption process. In symmetric cryptography key length is 64-256 bits while for the asymmetric algorithms the keys used are 256- 4096 bits. Since the way to get the key is from analyzing the plain-text and the ciphertext, for algorithms such as AES, it takes a very long time to calculate the result. Thus, they are considered quite secure.
On the other hand, the hacker who wants to reveal
the key in order to decrypt the information being
interested for, will find a way to this data. Since
the key is being stored in the memory, due to
system flaws or the effort of the hacker, it can be
disclosed. The resistance against the attacks or the
hacker’s efforts to gain access to the key is called
tamper resistance and is one of the most important
things to be considered while designing a
computer system [
Tamper resistance can be physical and logical. Since HSMs are tamper-resistant on both these sides, makes them a secure solution for data protection. There are many tests and mechanisms to detect either physical or logical tampering. HSM vendors, together with their product offer the tamper detection tools or functionalities too. Intel for example offers the possibility to enable the frequency, temperature and voltage detection features, offered together with the user’s guide to each method in order to customize his/ her own needs.
The Hardware Security Modules have a wide variety of uses that not only help in the encryption of information, but also ensure the data protection and security. Thus, there are some fundamental purposes in the HSMs usage such as:
HSMs, whether they are standalone
networkconnected or plug-in devices, have built-in random
number generators that provide randomness and
unpredictability of the keys [
An HSM encrypts the encryption keys in order to prevent the extraction of the plaintext, which would make the decryption process very easy. Furthermore, systems can use the encrypted keys even without having direct access to them [10]. Even more, the keys can be protected in all the workflow phases, production, testing and implementation. But it is suggested that the same HSM should not be used across different computing environments. Using a stand-alone HSM helps to prevent key exposure so the affected processes are more secure and protected.
Since the HSMs are stripped-down and standalone devices/ processors, they that can perform operations on their own. On the other hand, some types of HSMs are equipped to act as web traffic accelerator. As a result, behaving in such a way, offloading cryptographic operations and maintaining load balance, they improve the overall server performance.
Another important characteristic of the HSMs is that recently, with the development of technology and security policies, they are validated hardware components too. This ensures security compliance because, they meet specific industry standards. For example, as a typical computing device they provide logs that inform the host about different processes such as the cryptographic operations they are programmed to perform, the time when these operations were carried out, and the responsible party for authorizing the operations and processes.
According to NIST, the Hardware Security
Modules as critical key management components
of the physical infrastructure that makes secure
key storage and cryptographic operations possible
[
Cloud service providers and vendors, Banks, credit card companies and other financial institutions, Blockchain platforms and entities, Automotive manufacturers, Entertainment service providers, and IoT device developers and manufacturers. sector
The way how HSMs work is similar to a vending machine or an ATM, even though their purposes are totally different. Both vending machines or ATMs are isolated environments where things like food, drinks or money are kept. So, in order to take something from a machine, a person should at first put something in to take the desirable thing out; for example, put some coins in to take the food out, or put the card and withdraw the money back from the ATM. In this entire cycle, the involved person never changes or interferes with something else inside the machine. The HSM is also an isolated computing environment that accepts user inputs and generates outputs, but the user can neither see nor access the internal operations of the device that made the process go like it was intended. HSM generates for example a signed certificate, but the user cannot see, access or modify the cryptographic key that made it possible. All in all, what is enough for the user is the encryption keys safety, because data can be encrypted, yet information is not secure if the keys are exposed. If it is supposed for example that an authorized user exploits a system vulnerability and leaks sensitive data to the public, the private key that is used to secure the financial information of the company and its customers is being exposed. As a result, even if the information is encrypted, with the discovered key, the information is neither secure, not protected any more. This can be avoided if the keys are stored in a secure HSM, which will not only protect them, but also ensure strong security. But why should a company use a Hardware Security Module, when its cost is something to be considered and on the other hand web server’s architecture is supposed to offer some built-in functionalities that can also ensure protection? The answer is very simple. Since HSMs are isolated devices, with limited usage and as a result limited attack vectors too, they provide significantly more secure key storage than a traditional web server. Web servers are used to run many applications and functionalities and since the access is larger, the danger is on a larger scale too, because hackers have a higher chance to exploit the vulnerabilities. That is the reason why there are some industries where it is better to use the HSMs instead of a server’s security functionalities itself. As we stated before, companies use these devices to use and store the keys they use to sign their PKI certificates, software code and documents, to keep them more protected. Furthermore, public certificate authorities use these devices to create, store and manage their sensitive keypairs too.
3.1 HSM vs TPM
Hardware security modules are isolated hardware
components and tamper- and intrusion-resistant
devices that are used by organizations and
companies to store and protect cryptographic keys
[
As it is seen in the diagram above, there are four
main parts in the HSM’s physical and logical
architecture [
The control/ encryption module The control module performs operations like encryption, decryption or key management. Moreover, the control module uses Cipher Block Chaining (CBC) AES, a more complex version of AES for the encryption and decryption processes.
The power supply
According to Papa et al [
Random Number Generator module
The Hardware Random Number Generator, as it
was stated above is essential for this encryption
processes of a HSM. The HRNG does not use a
seed, but transistor uses a noise source to generate
random bits. In this case [
The tamper evidence module
This module will zeroize the key in two different
scenarios: when the casing has been removed or when
an attacker is drilling into the case [
Moore’s Law is a techno-economic model that has
enabled the IT industry to double the performance
and functionality of digital electronics roughly every
2 years within a fix cost, power and area [
As it was stated above, HSMs as dedicated and standalone or plug-in processors, specifically designed for the protection of the secret keys, are used by enterprises to protect secret information such as transactions, identities or financial data applications, by securing cryptographic operations, helping in encryption, decryption, authentication and digital signing services processes.
One of the most important uses of the HSMs is for
sure in card payment systems [
Another important feature to be discussed is that with the development of technology, there are a lot of options to choose. Nowadays HSMs come in a wide variety of options related to physical sizes and applications. Some of them can be small plugin cards or USB drives, while others are large external devices that should be stored and kept in secure locations. Hardware security modules can be very expensive because the initial price does not include other costs such as additional hardware, support, and maintenance. But, in case a company or organization cannot afford to buy one or more HSMs, it can use the cloud-based option, because some of the biggest HSM vendors like Amazon Web Services offer the cloud-based HSM’s products and services. When using cloud as such solution, a company can: Rent a physical HSM appliance that can be stored in the company’s off-site data center. Pay for access to the functionalities of an HSM vendor’s device or appliance. Pay for access to a virtual environment within a vendor’s shared HSM.
So, when it comes to using one of the options, or the other, there are advantages and disadvantages too. It is up to the company itself and what it needs for the work processes.
General Purpose Hardware Security Modules
In the General purpose HSM’s group are included
the HSMs that all the companies and
organizations globally use in the context of cyber
security. These devices are typically built
according to some specified cryptographic
principles, which emphasize how the HSM should
behave in specific scenarios and under specific
conditions, to ensure the functionalities are applied
[
One of the most important developments of the last
decades is quantum computing. It combines
information theory and quantum mechanics to create
a new era of computation and technology. According
to National Security Agency [
Even though recently quantum mechanics are still
being discovered and their implementation in the real
world’s applications is still low, laboratory
experiments have demonstrated quantum
computations with several quantum bits performing
dozens of quantum operations and this will totally
change the future. For now, it does not provide
efficient solutions to all problems. Strong limitations
on the power of quantum computation are known
since it has been proven that quantum computation
provides no significant advantage over classical
computation and yet, quantum information processing
has changed forever the way in which quantum
physics is understood [
From the cryptography and HSMs perspective, the development of quantum computing will also affect the future, but the first thing to be considered is that, since quantum computing technology is not yet in general use, what is discussed is like a projection for the future. Despite considering this, since the basic principle of quantum computing is creating a new kind of superperformant computational environment, different from the traditional and actual one, quantum computing will process huge amounts of data. This will therefore lead to major advances in cybersecurity, such as Quantum Key Distribution. As a result, quantum cryptography and its applications in encryption and decryption processes, will create stronger algorithms and eventually, stronger and unbreakable keys. On the contrary, application of quantum techniques can also be seen as a threat since it could be used to break cryptographic keys currently in use because current web applications are very vulnerable to quantum techniques. Yet, this is one of the greatest challenges of the future, to manage the process really well and to combine quantum techniques for stronger and more secure hardware and software components of the systems.
To sum up, HSMs are isolated hardware components that are used by companies and organizations to store, protect and secure the key used in the cryptographic operations that are being processed within the isolated computing environment. When discussing HSMs there are two main perspectives, security of the key and security of the data decrypted by the key. So, the HSM operates as "a separate server", where app server sends the encrypted data for decryption and the cleartext data comes back in the pp server. In this process, protecting the key is more important than protecting the data in packets, and this is what a HSM ensures.
As any other component of the system, using a HSM has its advantages and disadvantages too. A HSM can be quite expensive to purchase, maintain, and operate, and since they are usually priced on transaction throughput, the more data you need to decrypt at a time, the more expensive the HSM is. Furthermore, when buying an HSM, probably you as a company will spend a lot of time learning how to use it, how to perform key management and implementation into the existing systems.
On the other hand, if a company uses existing server’s functionalities in order to ensure data security or chooses to build its own server to perform the decryption of the data, it should make a lot of efforts to harden it against attacks, issuing certificates to authorized app servers, performing audits, managing security policies and so on. As a result, this will cost less than buying an HSM, but the key is still at more risk than in a HSM. Given all that, it is a matter of expenses vs risk and it is up to the company itself to choose the best option. Considering how critical the information is and if it is worth spending a certain amount of money on security, there comes a point when a decision should be made.
When it comes to the future, as time progresses, host CPUs tend to get faster, thanks to Moore’s Law, even though hardware stays the same, so the future trends have to consider this part, since complex cryptographic operations will need faster hardware devices too, the same way as the faster processors are implemented. Moreover, Quantum Computing and its future application in cryptographical algorithms and processes, will also affect the computational performance and security of HSMs.