IRJET- A Survey on Cryptography, Encryption and Compression Techniques

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 11 | Nov 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 3522
A Survey on Cryptography, Encryption and Compression Techniques.
Shiv Suraj Oberoi1, Yashika Varyani1, Dr. Deepak Chahal2
1MCA Student, Department of IT, Jagan Institute of Management Studies, Sector -05, Rohini, New Delhi. India
2Professor , Department of IT, Jagan Institute of Management Studies, Sector -05, Rohini, New Delhi. India
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Abstract: Data is any type of information that can be
stored digitally. Security of data is an aspect that comes
into play when the data which is digitally stored is to be
protected. Data security is one of the major factors of this
century, it refers to the protective measures taken to
prevent unauthorized access to the data stored in
personal computers, databases, and online websites or
cloud services. Cryptography is a concept which helps
the user to protect their data by giving them the
necessary tools and algorithms for encryption and
decryption of data.
Cryptography is a very popular way of sending/receiving
data in a very secretive way. Compression can be defined
as reducing the number of bytes required to represent a
set of data. Various techniques are used to reduce the
size of data depending on the requirement of the user.
Keywords: Data Encryption and decryption,
Compression, Cryptography Concept, Security, Integrity.
1. Introduction
Data can be defined as a collection of characters that is
organized to serve a purpose. It can be anything ranging
from text, number to images, videos. Raw data can be
defined as data in its most basic form. Raw Data becomes
“information” when it is processed and converted into a
form which is convenient for movement and processing.
In computing terms, Data can be described as a
collection of 1’s and 0’s which are called “bits”. A bit is
the smallest unit of data and a collection of eight bits is
called a “Byte”. Database can be defined as an organized
collection of data and Database Management System
where created to organize and manipulate the
information stored on it our main problem is the lack of
standardization regarding procedures and techniques.
Coming out of education and moving into the industry
you can find yourself with knowledge of various
methods and approaches, but no clear guide on best
practices [1].
Cryptography is the practise of generating ciphers which
are used to encrypt a message to ensure secure
communication between the sender and the receiver.
The encrypted message can only be decrypted by the
person for whom the information was intended.
Cryptography comprises of two very basic steps:
Encryption and Decryption. Encryption is performed at
the sender’s side and Decryption is done at the receiver’s
side.
Encryption is the process of converting information into
non-human readable format using an algorithm. It is the
process of applying cryptography. It is the process
through which plaintext can be converted into ciphertext
where the plaintext acts an input to the encryption
process and the ciphertext acts as an output to the
encryption process.
Decryption is a converse process of encryption; it
decrypts the encoded data into meaningful information.
It is the process through which ciphertext is converted
back to plaintext where the ciphertext acts an input to
the decryption process and the plaintext acts as an
output to the decryption process.
Data compression is a technique through which the size
of the data set is reduced by removing excessive
information and modifying the bit structure of data in
such a way that it acquires less space on the disk. Once
data compression is done, file maybe fully recovered
without any loss of actual information. Compressed data
files can be easily uploaded and downloaded from the
internet thus making the transfer of large sized files
easier.
Data compression techniques can broadly be divided
into two categories: Lossy techniques and Loss-less
techniques. In Lossy data compression, some part of the
data is removed while compressing it but in Loss-less
datacompression the same is achieved without the loss
of data.
In short, Data compression is the technique of encoding
data to lesser number of bits than the original
representation so that it requires less storage space and
can be easily shared between networks. A compression
tool is used to compress the data from and easy-to-use
format to one optimized of compactness.
Similarly, a decompression tool is used to restore
compressed data to its original form. Data
decompression is needed nearly in all cases of
compressed data including, lossy and lossless
compression.
2. Cryptography
Cryptography is usually referred to as “the study of
secret”. It is the transformation of understandable and
readable information into a form which cannot be
understood in-order to prevent data leakswith the helpof
a key and an algorithm. Cipher is the algorithm which is

used to convert plaintext to ciphertext, this method is
called “encryption”. Cryptograph covers three core areas
that protect us and our data from theft, unauthorized use
and possible fraud, these functions are usually referred
as the goals of the security system. These goals can be
listed under the following categories: Integrity,
Authentication, Confidentiality.
2.1 Integrity
Integrity of data refers to protecting information from
falsely being modified by an unauthorized party.
Information is valuable only if it is correct, tampered
information could prove costly to both the sender and
the receiver party. When sensitive data is being
exchanged between the sender and receiver, the receiver
must have the assurance that the message received has
not been tampered with and has been sent by the Sender
itself. There primarily two of threats in data integrity:
Passive and Active.
2.1.1 Passive Threat:
This type of threat happens when unintentional changes
happen in the data. The possibility of such errors
increases when there is noise in the communication
channel. Error correcting codes and methods like Cyclic
Redundancy Checks are used to detect loss of data
integrity. The victim remains unaware of the attack. In
passive attacks, attackers majorly observe the
transmission and tries to make use of the information
from the system but does not affect system resources.
2.1.2 Active Threats: In this type of threat, the attacker
attempts to alter system resources or effect their
operations. Active attacks involve some level of
modification to the data stream or tries to falsely tamper
with the data.The victim gets informed about the attack,
such attacks always cause some level of damage to the
system.
2.2 Confidentiality
The main aim of confidentiality is to ensure that the
information is not disclosed to unauthorized parties. It is
used to make sure that nobody between sender and the
receiver is able to what data or information is being
transmitted. This can only be achieved through
Encryption. There are two types of encryption
algorithms, Symmetric and Asymmetric. Symmetric
algorithms allow encrypting and decrypting data with
the same single key. Asymmetric algorithms have two
kinds of keys: Public and a Private key. The public key is
commonly available to the public and while the private
key is just available for each specific user. Everything
that is encrypted using the public key can only be
decrypted using the private key and vice versa.
2.3 Authentication
Authentication is the process of proving one’s identity or
it can be defined as the process of determining someone
is in fact who he claims to be. It is necessary for the
communication participants to prove their identities as
what they have claimed using some techniques so as to
ensure the authenticity [2]. This means that before
sending data or receiving data the identity of the sender
and the receiver must be verified.The authentication
process beings at the start of the application, the
incoming request is associated with a set of identifying
credentials. The credentials are often in the form of a
password, which is a secret and is known only to specific
individuals and the system. The process of
authentication can be distinctively be divided into two
phases: identification and actual
authentication.Identification phase provides a user an
identity on the security system in the form of an ID.
Identification and authentication are very similar the
only difference between them is, in identification the
user claims an identity by providing a usernameand in
authentication the user proves his identity by providing
a password.
3. Encryption
Encryption is a process in which an algorithm is used to
convert information into an unreadable format so that it
becomes useless for unauthorized parties. In an
encryption process, the information which is referred as
the “plain-text” is encrypted using and encryption
algorithm and a key, the encryption generates a “cipher
text” from the information which can only be read if it is
decrypted. This method protects useful information
about the user like credit card details and passwords by
encoding them and converting them into a cipher text.
Encryption is essential for safe and trusted exchange of
sensitive data. The process of building applications has
been a journey and it varies depending on one's
application requirements and purpose [3].
3.1 Types
Encryption algorithms can be categorized into two
categories: Symmetric encryption and Asymmetric
encryption.
Symmetric encryption algorithm, is also known as
“Private-key cryptography”. In this process there is only
one key which is used for both encryption and
decryption. Both the sender and the receiver each have a
copy of the key before the process of encryption and
decryption. The secret key could be a password/code or
a random string. At the sender side the plaintext is
encrypted and converted to ciphertext using the “key”
and the reverse of this process is done at the receiver’s
side where the ciphertext is decrypted and converted
back to plaintext using the “key” again. There are two
types of Symmetric encryption algorithm:Block

algorithms and Stream algorithms. In Block algorithms,
definite lengths of bits are encrypted in blocks of data
with use of a secret key. As the data is being encrypted,
the system holds the data in its memory. Examples of
Block algorithms are: Advanced Encryption standard
(AES), Data encryption standard (DES), International
data encryption algorithm(IDEA), BLOWFISH, Rivest
Cipher 5(RC5) and Rivest Cipher 6 (RC6).
In Stream algorithms, data is encrypted directly as it
streams instead of being retained in the system’s
memory. Example of Stream algorithms is: Rivest Cipher
4 (RC4).
Fig 1. Symmetric Cryptosystem
Asymmetric encryption algorithm, is also known as
“Public-key cryptography”, it uses two types of keys:
Public key and Private key. Public key is used to encrypt
the data and generate a ciphertext. The ciphertext is
decrypted by the receiver whenever it receives the
encrypted data by using it its own Private Key. Private
key is a secret key and is only known to the person who
the data is intended for and is unknown to all. Public
keys are stored in a database for anyone to see. There
are two types of Symmetric encryption algorithm: RSA
algorithms and Digital signatures.
Fig 2 Asymmetric cryptosystem
4. Data Compression
Data compression is a technique through which a file
(Text, audio or video) can be compressed, i.e. the size of
the file is reduced by removing the excessive information
and redundancy. Data compression is only considered
successful if the original file can be retrieved back with
any loss of information.
Data compression reduces file size considerably thus
saving storage space and making the transfer of such
files over the internet much easier as compressed files
can be uploaded or downloaded from the internet much
faster. Data compression has important in areas such as
File storage and Distributed system. Shorted data
sequences are more suitable for sending/ receiving
because it reduces the overall cost of transmission. Data
compression is particularly useful in communications
because it enables devices to transmit or store the same
amount of data in fewer bits. Data compression has two
components: Encoding Algorithm and Decoding
Algorithm. The Encoding Algorithm takes a message and
generates a compressed version of it and conversely the
Decoding algorithm reconstruct the original message
from the compressed version. A focus is made on
machines as machines cannot be understood by verbal
communication it forms abstractions and concepts [4].
4.1 Compression and Decompression
Data Compression techniques can be categorized into
two categories: Lossy Technique and Lossless Technique.
The algorithms which removes some part of data during
compression is called “Lossy Data compression” and the
algorithm which does not lose data while compressing
and is able to retrieve the same file after decompression
is called “Lossless Data compression”.
4.2 Types of Data Compression
In some applications loss of some amount of data is
acceptable, in such cases Lossy Compression technique is
used. The loss of data may be in the form of colour depth
or graphic detail. The best example for Lossy
compression technique is video conferencing. In video
conferencing considerable amount of data is lost in
transmission in order to deliver the image in real time.
Lossy compression targets redundant pixel information
and discards it. Lossy compression is majorly used with
media elements which can still work without all their
original data such as images, videos, audios and details
graphics which are used in screen designing.Lossy
Compression is not used for documents and software
because they need all of their data to be intact during
transmission.
Fig 3 Lossy Compression
In Lossless compression the data is compressed without
losing any amount of data. It reduces the size of file
without degrading the image quality. When the file is
decompressed, original data is retrieved. The data of the
file is only temporarily thrown away so that the
transmission of the file becomes easier. This type of
compression can be applied to not only just graphics but
to spreadsheets, documents and software application as
well because no amount of data will be lost in
transmission. While the advantage of this technique is
that the quality is maintained but the disadvantage of

this method is that it doesn’t reduce the size of the file
considerable.
Fig 4 Lossless Compression
5. Conclusions
This paper focuses on what data is, different encryption
and decryption techniques, Data compression and
various compression techniques.
Cryptography is used to encrypt data so that when the
data is sent over a network, so that it can be securely
transmitted and the contents of that message cannot be
altered with.
The main aim of data compression techniques is to
reduce the size of a file stored on the disk so that even
large sized files can be easily transferred on through a
digital network.
6. References
[1] Chahal D. et al. Data Science Applications, Challenges
Related Future Technology, International Journal of
Trend in Scientific Research and Development, Volume 3
Issue 1, Nov-Dec 2018
[2] Chahal D. et al. Security Concepts Underlying MANET,
International Journal of Emerging Technologies in
Engineering Research (IJETER), Volume 5 Issue 3, March
(2017).
[3] Kharb, L. (2018, January). A Perspective View on
Commercialization of Cognitive Computing. In 2018 8th
International Conference on Cloud Computing, Data
Science & Engineering (Confluence) (pp. 829-832). IEEE
[4] L. Kharb et al (2019) “Brain Emulation Machine Model
for Communication” in International Journal of Scientific
& Technology Research (IJSTR). pp 1410-1418

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