Cryptography 130919084510-phpapp02
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CRYPTOGRAPHY
Presented By : Shibani Sarangi
IT Branch, Regd no. 1001289324Guided By : Prof. X
Presented By : Ravinder KumarUID : 12MCA1051Vikas ChaudharyUID : 12MCA1073
Submitted To :Mrs. Shivani Jaswal Asst. Prof.
CRYPTOGRAPHY
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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. TYPES OF CRYPTOGRAPHY
Mainly classified into two types :
Symmetric key cryptography 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 Stream Block
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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2) MODERN: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.
http://en.wikipedia.org/wiki/Cryptography
https://www.coursera.org/course/crypto
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Thank
you….
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Thank
you….