This research analysis will go over the various encryption methods and summarize the previous research in encryption that has been done to this point. The advantages of Symmetric and Asymmetric Encryption will be discussed in terms of security and efficiency. As encryption becomes more advanced, so the need for proper key management increases as well. This paper will conclude with a look at what could be the future of cloud encryption, Homomorphic Encryption.

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Exploring the Cloud Encryption: The Past and the Future
Samuel A. Borthwick
CIT 516000: Database Security and Auditing
Dr. Xiao Luo
November 18, 2020

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Abstract
Cloud computing is becoming increasingly more common as a way for organizations to
work due to virtualization. Securing data over cloud is still a barrier many parties face when
deciding whether to adopt cloud. Encryption is a major component of security when working
with cloud databases. This research analysis will go over the various encryption methods and
summarize the previous research in encryption that has been done to this point. The advantages
of Symmetric and Asymmetric Encryption will be discussed in terms of security and efficiency.
As encryption becomes more advanced, so the need for proper key management increases as
well. This paper will conclude with a look at what could be the future of cloud encryption,
Homomorphic Encryption.
Exploring the Cloud Encryption: The Past and the Future
The emergence of Cloud computing has changed the way businesses have set up their IT
infrastructure. Salesforce’s article, 12 Benefits of Cloud Computing, references a study done by
the International Data Group that states “69% of businesses are already using cloud technology
in one capacity or another, and 18% say they plan to implement cloud-computing solutions at
some point” (12 Benefits of Cloud Computing, 2020). The benefits of using cloud computing are
tremendous and companies are starting to realize how vital it will be for their future. Cloud
computing, like that of web-based email, allows users to access all their files and applications
without having to keep the physical data on their own computers. The flexibility to not have an
established network infrastructure is not just a huge cost savings to companies, but it also serves
as a way for a much faster implementation by leasing Cloud data storage.
With the increased convenience of accessing data, comes an increased risk in security
threats as well as complex cloud-specific threats that may be unrecognizable to conventional
database administrators. If a business’s data can be accessed by its employees at any location, it
is reasonable to predict that cybercriminals will likely attempt to take advantage of this
increasingly popular system. The implications of a data leak from any company could have
devastating consequences. The CEO and President of IBM, Ginni Rometty, stated that
cybercrime, “Is the greatest threat to every profession, every industry, every company in the
world” (Rometty, 2015). A key role in cloud security is the encryption and decryption of data in
the cloud. This paper will provide a review of current cloud encryption research, analyze the
various encryption methods that apply to cloud computing, and go over best practices.
Literature Review
A View About Cloud Data Security from Data Life Cycle
This publication by Xiaojun Yu and Qiaoyan Wen details how data security has become
the central problem of cloud computing (Yu, 2010). The authors make the argument that that

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cloud data security should be solved from the data life cycle. The data life cycle model they refer
to, as shown in Figure 1, includes 5 stages: create, store, Use and share, archive, and destruct.
Figure 1. Data Life Cycle Model
Internal threats are most likely to com from cloud service providers and users of the clous where
external threats can come anywhere (Yu, 2010). As soon as data is generated, that is when risks
are present. The adversary could do several things from data tampering to editing the access
controls. Stored data presents the most risks, as this is when the data is the most vulnerable.
Information has the potential to leak while creating a backup. Sharing data further poses a risk
due to the means of transmitting the data. The archive stage is often safer due to the data not
being used temporarily, but until data is completely destroyed in the destruct phase, threats still
pose a risk.
Yu’s premise is based off taking the following five steps when initiating the general data
security process (Yu, 2010):
1. The user classifies data with sensitivity level as it is created.
2. The user then stored data into the cloud via contact with a cloud sever. The client should
encrypt the data before sending it to the cloud server proxy or build a secure link in
which the data is stored to the cloud.
3. Data that is not actively being used is archived.
4. When transmitting data, the cloud server proxy gives proof of data integrity to the client.
If integrity of data is intact, key management is then initiated to start the transmission of
data
5. When the data is no longer needed, the client sends a data destroy request to the cloud
proxy who will then initiate the process of destroying data, followed by sending back
proof to the client. This step to include key management between the client and cloud
proxy, so that vital information is not deleted from internal or external threats.
Cryptography in Cloud Computing: A Basic Approach to Ensure Security in Cloud
Rishav Chatterjee is his research article, Cryptography in Cloud Computing: A Basic
Approach to Ensure Security in Cloud, gives an overview of the benefits of cloud computing that
make it so attractive to companies. Cloud computing requires no underlying infrastructure and
follows a user-friendly model that only requires payment for storage used (Chatterjee, 2017).

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Furthermore, it allows for virtualization of physical resources and wide accessibility that was not
previously obtainable. According to Chatterjee, there are two unique groups of models:
deployment models and service models. The deployment model consists of Private cloud, Public
cloud, and a hybrid of both. Service models on the other hand consist of Iaas, Saas, and Paas.
While the benefits of cloud are overwhelming, privacy and security remain a concern.
Different types of service models under cloud computing offer different levels of security
services. Iaas (Infrastructure as a Service) offers the minimum security, while Saas offers the
highest level of security. This paper looks at the various algorithms in encryption including
Symmetric, Asymmetric, and Hashing. and encryption techniques. Brief summaries of
encryption techniques are provided for Advanced Encryption Standard, Blowfish Algorithm,
Data Encryption Standard, and RSA Cryptosystem. The research article ends with discussing the
most prominent problems facing cloud computing such as data theft, data integrity, loss of data,
and location of data.
Homomorphic Encryption for Data Security in Cloud Computing
Traditional standard encryption methods provide security during data storage and data
transmission (Chauthan, 2015). Encryption for data in the processing state has not been possible
without first decryption. This poses a great security risk for cloud computing and has since been
a barrier to organizations considering the transfer to cloud. The reason this is a concern is
because data confidentiality must be forfeited for any operations (totals, averages, standard
deviations) to be performed on the data. The author of this research paper, Kamal Chauhan,
argues that the solution to this problem would be to perform operations on data that is currently
encrypted on the cloud server. This type of encryption is referred to as Homomorphic
Encryption.
The homomorphic encryption technique allows the user to operate ciphertext directly.
The user can decrypt the results of the cipher and see that it matches the same as if operations
were carried out in plaintext. While this has the potential to change cloud security for the better,
it still is developing and currently carries several obstacles. It is very inefficient in the amount of
time it takes to complete operations. Furthermore, the amount of operations that can be done are
very limited. More computing power is needed for this encryption to be rolled out on a massive
scale.
Data Security and Privacy in Cloud Storage using Hybrid Symmetric Encryption Algorithm
Dr. Arockiam notes in this research paper, that while cloud computing is transformative
in its ability to store massive amounts of data and centralize data warehouses, it does leave room
for opportunistic cyber thieves (Arockiam, 2013). Many research problems are yet to be
identified, giving leverage to criminal behavior as the rush to both harm and defend cloud
databases intensifies. Dr. Arockiam identifies Symmetric encryption as best suited for handling
large volumes of data efficiently in cloud storage. This paper also proposes an algorithm
improving on classical encryption techniques by integrating substitution cipher and transposition
cipher. Dr. Arockiam describes the algorithm:

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“In the proposed algorithm, initially the plain text is converted into corresponding ASCII
code value of each alphabet. In classical encryption technique, the key value ranges between 1 to
26 or key may be string (combination alphabets). But in proposed algorithm, key value range
between 1 to 256. This algorithm is used to encrypt the data of the user in the clouds. Since the
user has no control over the data after his session is logged out, the encryption key acts as the
primary authentication for the user” (Arockiam, 2013).
Data Security and Privacy Protection Issues in Cloud Computing
This paper by Deyan Chen provides an overview of some of the challenges in security
facing cloud computing as well as current solutions. According to a survey from IDCI in 2009,
74% IT managers and CIOs believed that the primary challenge that hinders them from using
cloud computing services is cloud computing security issues (Chen, 2012). Choosing the right
vendor can sometimes be challenging, as different vendors offer different levels of security and
understanding the differences can be difficult to comprehend. Figure 2 shows a visual of cloud
computing security architecture.
Figure 2. Cloud Computing Security Architecture
Key management, as Chen points out turns into a major issue. Not every company has the
infrastructure to manage massive amounts of keys with the type of protocols that advanced
encryption requires. Ultimately Chen believes a fully homomorphic encryption scheme, like that
developed by IBM, would solve the majority of problems facing cloud security by allowing data
to remain encrypted while being processed.
Encryption Methodologies
This section outlines the two main types of encryption classifications, symmetric and
asymmetric, and gets into specific encryption techniques. A breakdown of homomorphic
encryption will be given and an analysis on its future implications. Due to the importance of key
management, best practices will be discussed in this section as well.

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Symmetric Encryption
Symmetric encryption (see Figure 3) involves the use of one single key for both
encryption and decryption (Arockiam, 2013).
Figure 3. Symmetric Encryption
For example, a source would produce a message in plaintext. The encrypt, a key is the generated
at the message source and provided to the destination through a secure channel for decryption.
Because Symmetric Encryption only requires one key and is the more simplistic form of
encryption, it is much faster method than asymmetric, and is almost exclusively used to transmit
data in bulk. It requires much less computational power than asymmetric and because of this, is
much more cost-efficient.
DES. The Data Encryption Standard (DES) is a block cipher developed in 1977 by the
National Institute of Standards (Chatterjee, 2017). At the encryption site, DES takes 64-bit
plaintext and creates 64-bit cipher text. During decryption, 64-bit cipher text is created back to
64-bit plaintext, so both the cipher and plaintext stay at 64-bit throughout the entire process. The
key however is a 56-bit cipher key used for both encryption and decryption. Encryption takes
place in two permutations, initial and final permutation. There are sixteen different rounds
throughout encryption and each round uses a different sort of 48-bit key which is generated from
the cipher key based on a predefined algorithm. See Figure 5.

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Figure 4. DES Architecture
AES. Advanced Encryption Standard (AES) is a symmetric key algorithm. Each of the
ciphers has a 128-bit block size with key sizes of 128, 192, and 256 bits (Chatterjee, 2017). See
Figure 5.
Figure 5. AES Architecture
With AES, rows are shifted in a transposition step where each row is shifted a certain number of
steps. Columns are mixed, combining the four bytes in each column. The key that is generated
follows the shifts in the rows and mixed columns to generate a key that is used for both
encryption and decryption, as it is symmetric. The National Institute of Standards developed
AES in 1997 for the U.S. government (Rouse, 2020).
AES VS DES. AES was developed largely to replace DES in securing classified
information for the US government.
The time required to crack an encryption algorithm is directly related to the length of the key
used to secure the communication (Rouse, 2020).

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AES has much larger key sizes—128-bit, 192-bit, and 256-bit, making it much stronger than the
56-bit key of DES.
Asymmetric Encryption
In Asymmetric Encryption, different keys are used for encryption and decryption. Each
of the receivers have their own key for decryption, known as their private key. Receivers share a
key for encryption, known as the public key. Due to this two-key architecture, Asymmetric has a
much higher level of security. Common applications for Asymmetric Encryption include
blockchain, text communication, and intellectual property. See Figure 6.
Figure 6. Asymmetric Encryption
RSA. The oldest and still most used asymmetric cryptosystem is RSA encryption
(Chatterjee, 2017). Considered the most secure used method of encryption, RSA involves two
keys, the private key and the public key. In the verification process, the server implements
authentication of the public key by signing a unique message known as the digital signature. The
use of a digital signature allows for further security. The key sizes for RSA are far larger (512-
bit, 1024-bit, 2048-bit, 3072-bit, and 4096-bit) than those of Symmetric methods making it far
more secure.
Homomorphic Encryption
A current limitation to cloud computing is that encryption can only be applied to data that
is in a storage state or transmission state. Homomorphic Encryption allows data to be processed
while still in an encrypted state (Chauhan, 2015). For example, plain text of 5 and 10 could be
encrypted to X and YZ. X and YZ could then be added together to form (X+YZ). No party
would ever know the value of (X+YZ) is equal to 15, because they would only be able to see the
encrypted text, X and YZ. Only until the final step of decryption, would the receiver know that
(X+YZ) =15. See Figure 7.

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Figure 7. Homomorphic Encryption Example
Because the level of computational power required for Homomorphic Encryption is
tremendous, Homomorphic is still very young in its development and is not able to be adopted
widely. The biggest benefit Homomorphic Encryption could potentially have, is allowing parties
to share data with each other, while still protecting each party’s individual data from being
revealed. A practical application would include free elections where votes could be added up
while keeping the results of each vote private, allowing for a more secure and transparent
election process. Currently IBM and Microsoft are working to speed up the process of
Homomorphic Encryption in hopes that it can soon be deployed on a much larger scale.
Key Management Best Practices
Encryption, both Symmetric and Asymmetric, is only as reliable as the security of its
keys. Symmetric is more vulnerable since the same key is used for encryption and decryption.
Key management can be a challenge for many parties with the complexity of key protocols. Best
practices should include:
• Centralize Encryption key management systems
• Use automation to rotate keys at set intervals
• Keep strict logging and auditing of encryption key use
• Create an Encryption Key Management Policy for Employees
• Rotate Your Keys
Companies should adopt centralized, in-house key management policies. However, many
companies and organizations may not have the underlying infrastructure, so hiring a third-party

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key management service may be required. By centralizing encryption keys, it minimizes the
number of places where keys can get exposed to attackers.
Conclusion and Future Scope
Cloud computing is emerging as a standard practice in information technology for
companies and organizations across the globe. As it becomes more common place, so will the
need to secure against current known threats and unknown threats that have yet to be determined.
Ultimately encryption is the best defense against cyber criminals attacking the cloud. The two
distinct encryption algorithms are Symmetric and Asymmetric. Symmetric is highly efficient and
is best for transmitting data in bulk, where Asymmetric offers a much higher level of security
through a public and private key. Best practices and set policies should be used when
approaching key management. Homomorphic Encryption offers a large scope possibility of
future improvement and still early in development. Finding ways to decrease the amount of
computational overhead for Homomorphic to be efficient, leaves much research for the future.
Advances in machine learning are a likely avenue for Homomorphic and need to be investigated.

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