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CRYPTOGRAPHY

Submitted in partial fulfillment of the

Requirements for the award of the degree of

Bachelor of Technology

In

Computer Science & Engineering

By:

GAGANDEEP SINGH (0651322708/CSE1/2008)

GAGANDEEP KAUR(0661322708/CSE1/2008)

ISHDEEP SINGH(00913207209/CSE1/2008)

Department of Computer Science & Engineering

Guru Tegh Bahadur Institute of Technology

Guru Gobind Singh IndraprasthaUniversity

Dwarka,New Delhi


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What is CRYPTOGRAPHY?yCryptography, a word with Greek origins,

means SECRET WRITING.

yIt is the science of writing messages insecret codes.

yIt is a process to encrypt sensitive

information to protect your privacy.


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Components of Cryptographyy PLAIN TEXT

It is original message ,before being transformed. The data

are not encrypted.y CIPHERTEXT

After the message is transformed . The data are encrypted.

y Alice

Alice is the person who needs to send secure data.

y Bob

Bob is the recipient of the data.


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y

EveEve is the person who somehow disturbs the

communication betweenAlice and Bob.

y ENCRYPTION

Encryption is the conversion of data into a form, called acipher text that cannot be easily understood by

unauthorized people.

y DECRYPTION

It is the process of converting encrypted data back into itsoriginal form, so it can be understood.


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Process of Cryptography


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Types of Cryptographyy Symmetric key cryptography

In symmetric key cryptography, the same key is used by the

sender(for Encryption) and the receiver(for Decryption) . Thekey used is called Public key.

y Asymmetric key cryptography

In asymmetric key cryptography, two types of keys are used.

Different keys are used by both sender and receiver.

The key used is called Private key.


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MODES OF ENCRYPTION OR DECRYPTION

yManual mode

In this mode user selects the algorithm for encryption

or decryption.

y Dynamic mode

In this mode system itself selects the algorithm for

encryption or decryption randomly.


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ALGORITHMS USED FOR ENCRYPTION AND

DECRYPTION

y DES: DATAENCRYPTION STANDARDS

DES encrypts and decrypts at the bit level.The plain text are broken into segments of 64 bits. Each sectionis encrypted using a 56-bit key. It is very difficult to guess the

bits of plaintext from the bits of ciphertext.

y BLOWFISH

Blowfish has a 64-bit block size and a variable key length

from 32 bits to 448. While doing key scheduling, it generateslarge pseudo-random lookup tables by doing severalencryptions. It is not a good choice when a large memory spaceis not available.


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y TES (Triple DES)

It is a variation of Data Encryption Standard (DES). It uses a

64-bit key consisting of 56 effective key bits and 8 parity bits.

The size of the block for Triple-DES is 8 bytes. It improves the

security of DES by applying DES encryption three times using

three different keys. Triple DES algorithm is very secure, but itis also very slow.

y XOR

XORcipher is a simple encryption algorithm that operates

according to the principles of XOR. With this logic, a string oftext can be encrypted by applying the bitwise XORoperator to

every character using a given key. To decrypt the output,

merely reapplying the key will remove the cipher.


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Message digest

y Message-DigestAlgorithm is a widely used cryptographic

hash function that produces a 128-bit (16-byte) hash

value. It has been employed in a wide variety of securityapplications, and is also commonly used to check data

integrity. However, it has been shown thatMD is not

collision resistant, so it is not suitable for applications like

digital signatures that rely on this property.AnMD hash is

typically expressed as a 32-digit hexadecimal number.

y It was designed by Ron Rivest in 1991.


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Applications Of Cryptographyy Privacy & Security : E-mail message, Wireless networkA company may have information that a competitor would like to see, suchas information concerning legal or financial problems

y Confidentiality : Personal records, Transaction recordsCompanies often possess data files on employees which are confidential,such as medical records, salary records, etc. Employees will feel saferknowing that these files are encrypted and are not accessible to casualinspection. It also enables you to encrypt sensitive data, such as credit cardnumbers

y Authentication : Digital signatures, LoginIt enable users to sign the electronic documents digitally and encrypt themwhich assures the user of data integrity, confidentiality, security and non-

repudiation of documents and transactions.


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y Intellectual Property : Copy protection

It prevent the illegal copying or use of computer software and data.

One method is the EXE wrapper which will take an EXE and create an

encrypted version of the software. It can only be decrypted through the copy

protection wrapper.


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Advantagesy Ease-of-use - It is easy to understand.

y Reliability- It means that when used as its designer

intended it to be used, will always reveal exactly theinformation hidden when it is needed (in other words, that

the ciphertext will always be recoverable and the

recovered data will be the same as to the original

plaintext).y Security - It means that it will keep the information hidden

from all but those persons intended to see it despite the

attempts of others to crack the system.


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y The number of the keys is only twice of the number of

user.

y Individuals can post their public key on their Web site.


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Disadvantagesy The complexity of the algorithm.

y Calculating the ciphertext from plaintext using the long

keys takes a lot of time.y Disadvantage of public key systems is that there is a

problem of key validation.

y Encryption Does Not ProtectAgainst aMalicious DBA.


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Conclusiony The primary objective of this system is to protect confidential documents.

y Cryptography helps to store confidential data of any size.

y DES, Triple DES, Blowfish and XORalgorithms are fast and are well suitedfor performing cryptographic transformations on large streams of data.

y It is a very easy process of securing important data.

y Scope of the project is not only to meet the needs of an organisation but alsoon individual needs.

y The proposed system achieves the following goals:

Confidentiality

Data integrityAuthentication


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Referencesy Applied Cryptography by Bruce Schneier

y Handbook ofApplied Cryptography byA.J.Menezes and

P.C.Van Oorschoty Modern Cryptography by P.Rogaway

y en.wikipedia.org/wiki/cryptography

y cryptocode.wordpress.com/


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Thank you

Date post:	06-Apr-2018
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