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CRYPTOGRAPHY

Presented By : Shibani Sarangi

IT Branch, Regd no. 1001289324Guided By : Prof. X

Presented By : Sidharth MahapatraECE Branch, Regd no. 0901298191

CRYPTOGRAPHY

Guided By : Asst. Prof. Smita Mohanty

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OVERVIEW

Cryptography Vocabulary Encryption &

Decryption Transmission

Technique Symmetric

Cryptography Asymmetric

Cryptography Conclusion References

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WHAT IS CRYPTOGRAPHY ?

Cryptography is the science of using mathematics to encrypt and decrypt data.

Cryptography enables you to store sensitive information or transmit it across insecure networks so that it cannot be read by anyone except the intended recipient.

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VOCABULARY

Plaintext: Data that can be read and understood without any special measures.

Encryption: The method of disguising plaintext in such a way as to hide its substance is called encryption.

Cipher text: Encrypting plaintext results in unreadable gibberish called cipher text.

Decryption: The process of reverting cipher text to its original plaintext is called decryption.

Key: some secret piece of information that customizes how the cipher text is produced.

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VOCABULARY

Cryptanalysis: The art of breaking ciphers, i.e. retrieving the plaintext without knowing the proper key.

Cryptographers: People who do cryptography

Cryptanalysts: Practitioners of cryptanalysis.

Cryptology: The branch of mathematics that studies the mathematical foundations of cryptographic methods.

Cipher: The Encoder, i.e., the encryption/decryption scheme

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ENCRYPTION & DECRYPTION

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WHY USE CRYPTOGRAPHY ?

For “secret writing” To establish a shared secret when

other people (eavesdroppers) are listening.

TYPESMainly classified into two types :

1. Symmetric key cryptography2. Asymmetric key

cryptography

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TRANSMISSION TECHNIQUE

encoderdecoder

(plaintext in -ciphertext out)

ciphertext ciphertext msgmsg

(ciphertext in- plaintext out)

(should understandnothingnothingabout themsg)

eavesdropper

bla-blabla-bla

cmbcmb--cmbcmb bla-blabla-bla

Cipher msg

Plain text – inCipher text -

out

Should understand NOTHING about the

message

Cipher text – inPlain text - out

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Cryptography

Symmetric key Asymmetric key cryptography cryptography (Public key cryptography)

Classical

Modern cryptography cryptography

Transposition Substitution StreamBlock

cipher cipher cipher cipher

CLASSIFICATION

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SYMMETRIC KEY CRYPTOGRAPHY

BOTH SHOULD KNOW THE KEY

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TRANSPOSITION CIPHER

In classical cryptography, a transposition cipher changes one character from the plaintext to another i.e. the order of the characters is changed.

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SUBSTITUTION CIPHER

Substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system.

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STREAM CIPHER

A Stream Cipher is a symmetric or secret-key encryption algorithm that encrypts a single bit at a time. With a Stream Cipher, the same plaintext bit or byte will encrypt to a different bit or byte every time it is encrypted.

e.g. :Plain text: Pay 100Binary of plain text: 010111101

(hypothetical)Key: 100101011

----- Perform XOR____________________

Cipher text 110010110 ----- ZTU9^%D

To decrypt make the XOR operation of the cipher text with the key .

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BLOCK CIPHER

Block cipher technique involves encryption of one block of text at a time .Decryption also takes one block of encrypted text at a time. Length of the block is usually 64 or 128 bits.

e.g. :Plain text: four and fiveFour and fiveKey Key Keywvfa ast wvfa ---

cipher text

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ASYMMETRIC KEY CRYPTOGRAPHY

Public key cryptography is an asymmetric scheme that uses a Pair of keys for encryption: a Public key, which encrypts data, and a corresponding Private key (secret key) for decryption.

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CRYPTANALYSIS

Cryptanalysis refers to the study of ciphers, cipher text, or cryptosystems (that is, to secret code systems) with a view to finding weaknesses in them that will permit retrieval of the plain text from the cipher text, without necessarily knowing the key or the algorithm. This is known as breaking the cipher, cipher text, or cryptosystem.Unlike cryptography which is a clearly defined science, Cryptanalysis is as much an art as it is a science.

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CRYPTANALYSIS TECHNIQUES

Known - plain text analysis

Chosen – plain text analysis (Differential cryptanalysis)

Cipher text - only analysis

Man – in – the - middle attack

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ACOUSTIC CRYPTANALYSIS

It is a side channel attack which exploits sounds emitted by computers or machines. Modern acoustic cryptanalysis mostly

focuses on sounds emitted by computer keyboards and internal computer components Historically it has also been applied to

impact printers and electromechanical cipher machines.

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COUNTER MEASURES

Use rubber keyboard or virtual keyboards to prevent keystroke sounds. Use acoustic printers. Use Acoustic case for CPU.

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CONCLUSION

Cryptography, being an art of encrypting and decrypting confidential information and private messages, should be implemented in the network security to prevent any leakage and threat. It can be done by using any of these

techniques discussed above for fortifying the personal data transmission as well as for secure transaction. Acoustic cryptanalysis, being an art of

decrypting or leaking confidential information from the sound generated from the CPU, Keyboard, printers, etc may be used in both constructive as well as destructive ways.

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REFERENCE

Yang, Sarah (14 September 2005), "Researchers recover typed text using audio recording of keystrokes", UC Berkeley News.

Adi Shamir & Eran Tromer. "Acoustic cryptanalysis". Blavatnik School of Computer Science, Tel Aviv University. Retrieved 1 November 2011.

http://en.wikipedia.org/wiki/Cryptography

https://www.coursera.org/course/crypto

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Thank

you….