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# Cryptography

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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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### Cryptography

1. 1. Presented By : Shibani Sarangi IT Branch, Regd no. 1001289324 Guided By : Prof. X 1
2. 2. 2 Cryptography Vocabulary Encryption & Decryption Transmission Technique Symmetric Cryptography Asymmetric Cryptography
3. 3. 3 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.
4. 4. 4 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
5. 5. 5 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.
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7. 7. 7 For “secret writing” To establish a shared secret when other people (eavesdroppers) are listening. TYPES Mainly classified into two types : 1. Symmetric key cryptography 2. Asymmetric key cryptography
8. 8. 8 encoder decoder (plaintext in - ciphertext out) ciphertextciphertext msgmsg (ciphertext in - plaintext out) (should understand nothingnothing about the msg) eavesdropper bla-blabla-bla cmbcmb--cmbcmb bla-blabla-bla Cipher msg Plain text – in Cipher text - out Should understand NOTHING about the message Cipher text – in Plain text - out
9. 9. Cryptography Symmetric key Asymmetric key cryptography cryptography (Public key cryptography) Classical Modern cryptography cryptography Transposition Substitution Stream Block cipher cipher cipher cipher 9
10. 10. BOTH SHOULD KNOWTHE KEY 10
11. 11. 11 In classical cryptography, a transposition cipher changes one character from the plaintext to another i.e. the order of the characters is changed.
12. 12. 12 Substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system.
13. 13. 13 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 100 Binary of plain text: 010111101 (hypothetical) Key: 100101011 ----- Perform XOR ____________________ Cipher text 110010110 -----
14. 14. 14 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 five Four and five Key Key Key wvfa ast wvfa ---
15. 15. 15 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.
16. 16. 16 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
17. 17. 17 Known - plain text analysis Chosen – plain text analysis (Differential cryptanalysis) Cipher text - only analysis Man – in – the - middle attack
18. 18. 18 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.
19. 19. 19 Use rubber keyboard or virtual keyboards to prevent keystroke sounds. Use acoustic printers. Use Acoustic case for CPU.
20. 20. 20 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
21. 21. 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 21
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