CRYPTOGRAPHY

CRYPTOGRAPHY

Presented By : Shibani SarangiIT Branch, Regd no. 1001289324Guided By : Prof. X

Presented By : Sidharth MahapatraECE Branch, Regd no. 0901298191CRYPTOGRAPHYGuided By : Asst. Prof. Smita Mohanty1

overview

2 Cryptography Vocabulary Encryption & Decryption Transmission Technique Symmetric Cryptography Asymmetric Cryptography Conclusion References

What is cryptography ?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.

vocabulary4 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.

vocabulary5 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

Encryption & Decryption

6

Why use cryptography ?7 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

Transmission technique8

Cipher msgPlain text inCipher text - outShould understand NOTHING about the messageCipher text inPlain text - out

Cryptography

Symmetric key Asymmetric key cryptography cryptography (Public key cryptography)

Classical Modern cryptography cryptography

Transposition SubstitutionStreamBlock cipher cipher cipher cipherclassification9

Symmetric key cryptographyBOTH SHOULD KNOW THE KEY10

Transposition cipher11 In classical cryptography, a transposition cipher changes one character from the plaintext to another i.e. the order of the characters is changed.

substitution cipher12 Substitution cipher is a method of encryption by which units of plaintext are substituted with ciphertext according to a regular system.

Stream cipher13 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 .

Block cipher14 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

Asymmetric key cryptography 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.

cryptanalysis16Cryptanalysis 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 textfrom the cipher text, without necessarily knowing thekeyor thealgorithm. This is known asbreakingthe cipher, cipher text, or cryptosystem.Unlike cryptography which is a clearly defined science, Cryptanalysis is as much an art as it is a science.

Cryptanalysis Techniques17 Known - plain text analysis

Chosen plain text analysis (Differential cryptanalysis)

Cipher text - only analysis

Man in the - middle attack

acoustic cryptanalysis18 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.

Counter measures19 Use rubber keyboard or virtual keyboards to prevent keystroke sounds. Use acoustic printers. Use Acoustic case for CPU.

conclusion20 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.

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

21

Thank you.22