cryptography presented by : nilay jayswal branch : computer science & engineering entry no. :...
TRANSCRIPT
1
CRYPTOGRAPHY
PRESENTED BY : NILAY JAYSWAL
BRANCH : COMPUTER SCIENCE & ENGINEERING
ENTRY NO. : 14BCS033
2OVERVIEW
Cryptography Vocabulary Encryption and Decryption Transmission Technique Symmetric Cryptography Asymmetric Cryptography Conclusion
3What is Cryptography ?
Cryptography is the science of using mathematics to encrypt and decrypt data.
Benefit ?
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.
4VOCABULARY
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
5…continued
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
6ENCRYPTION & DECRYPTION
• encryptionplaintext
• decryptionciphertex
t
plaintext
7Why Cryptography ?
For “secret writing” To establish a shared secret when other people
(eavesdroppers) are listening.
Types of Cryptography
1. Symmetric key cryptography
2. Asymmetric key cryptography
8Transmission Technique
Sender
Plaintext in Encoder
Ciphertext out Eavesdroppe
r
Ciphertext in Decoder
Plaintext in Receiver
9CLASSIFICATION
Cryptography
Symmetric Key Cryptography
Asymmetric Key
Cryptograph
10Symmetric
Key Cryptography
Classical Approach
Modern Approach
Classical Approach
Transposition Cipher
Substitution Cipher
Modern Approach
Stream Cipher Block Cipher
11SYMMETRIC KEY CRYPTOGRPHY
Symmetric Key Cryptography are algorithms for that use the same key for both encryption of plaintext and decryption of ciphertext. They may be identical or there may be a simple transformation to go between the two.
Plai
ntex
t
Encr
yption
Ke
y “
X “
Cip
hert
ext
Dec
rypt
ion
Key
“ X ”
Plai
ntex
t
12TRANSPOSITION CIPHER
In classical cryptography, a transposition cipher changes one character from the plaintext to another
i.e. the order of the characters is changed
e.g.
1 2 3 4 5 6 7 8 9
Plaintext : T O P S E C R E T
Ciphertext : 2 1 4 3 5 7 6 8 9
O T S P E R C T E
13SUBSTITUTION CIPHER
Substitution cipher is a method of encryption by which units of plaintext are substituted with
ciphertext according to a regular system.
e.g.
Plaintext : A B C D X Y Z
Ciphertext : A B C D E F X Y Z
14STREAM 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 XORCipher text : 110010110
15BLOCK 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 five
Four and five
Key Key Key
wvfa ast wvfe
Ciphertext : wvfa ast wvfe
16ASYMMETRIC KEY CRYPTOGRAPHY
Asymmetric 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) .
Plai
ntex
t
Encr
yption
: Pu
blic
Key
Cip
hert
ext
Dec
rypt
ion
: Pr
ivat
e ke
y
Plai
ntex
t
17CRYPTANALYSIS
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.
18Cryptanalysis Techniques
Known - plain text analysis
Chosen – plain text analysis (Differential cryptanalysis)
Cipher text - only analysis
Man – in – the - middle attack
19ACOUSTIC 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.
20CONCLUSION
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
21REFERENCE
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…
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Q & A