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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