Understanding Cryptography and Cipher Techniques
Dive into the world of cryptography with a focus on classic cipher techniques like the Caesar cipher and Vigenère cipher. Explore modern encryption algorithms such as AES and RSA, along with discussions on security concepts like cryptanalysis and cryptographic attacks. Discover how cryptography helps protect confidentiality and integrity in information security.
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Presentation Transcript
IT 6823 LM 6 Cryptography Dr. Lei Li
NIST Framework Core Image source: https://www.nist.gov/document/cybersecurityframeworkv1- 1presentationpptx IT 6823 LM6 Cryptography 2
Learning Outcomes Define cryptography and its main concepts Describe the Caser cipher and Vigen re cipher Discuss AES algorithm and its applications Explain Public Key Cryptography Describe the RSA algorithm Discuss security through obscurity Explain what s cryptanalysis and cryptographic attacks IT 6823 LM6 Cryptography 3
Cryptography Protect confidentiality and integrity Image source: https://searchsecurity.techtarget.com/definition/cryptography IT 6823 LM6 Cryptography 4
Cipher Types Stream cipher Encrypt 1 byte at a time Simple and fast Block cipher Encrypt one block at time Complex and secure IT 6823 LM6 Cryptography 5
Classic Cryptography Focus on confidentiality Sender, receiver share common key Keys may be the same, or trivial to derive from one another Sometimes called symmetric cryptography Transposition cipher Substitution cipher Caesar cipher IT 6823 LM6 Cryptography 6
Caesar Cipher One of the simplest and most widely known Image source: https://en.wikipedia.org/wiki/Caesar_cipher IT 6823 LM6 Cryptography 7
Caesar Cipher Example Cipher key Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ Cipher: XYZABCDEFGHIJKLMNOPQRSTUVW Encryption Plaintext: THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG Ciphertext: QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD IT 6823 LM6 Cryptography 8
Breaking Caesar Cipher Brute force attack Test out all possible shifts Frequency analysis Distribution of English language text has distinctive and predictable shape IT 6823 LM6 Cryptography 9
Vignere Cipher Has several Caesar Ciphers in sequence with different shift value Vig nere table Disguise the plaintext letter frequency Weakness Repeat nature of the key IT 6823 LM6 Cryptography 10
Vignere Cipher - Example Plaintext: ATTACKATDAWN Key: LEMONLEMONLE Ciphertext: LXFOPVEFRNHR IT 6823 LM6 Cryptography 11
Advanced Encryption Stand (AES) Modern symmetric-kay algorithm Supersedes Data Encryption Standard (DES) Announced by NIST in 2001 Key size: 128, 192 and 256 bits. Fast & highly secure IT 6823 LM6 Cryptography 12
AES Applications Web communication Wi-Fi (can be used as part of WPA2) Mobile apps (such as WhatsApp and LastPass) Native Processor Support Libraries in many software development languages VPN Implementations Check encryption used by a website: https://www.ssllabs.com/ssltest/ IT 6823 LM6 Cryptography 13
Public Key Cryptography Asymmetric cryptography A pair of keys Public key maybe disseminated widely Private keys known only to owner Based on mathematical one-way function Solve the key exchange in unsecure channel an issue for symmetric key cryptography PKI IT 6823 LM6 Cryptography 14
Public Key in Action Image source: https://en.wikipedia.org/wiki/Public-key_cryptography IT 6823 LM6 Cryptography 15
RSA Cryptosystem Widely used public-key cryptosystem Given function (me)d mod n = m e, d, and n very large positive integers Knowing e and n, or even m, it can be very difficult to find d IT 6823 LM6 Cryptography 16
RSA Algorithm Choose two large prime numbers p, q Let n = pq; then (n) = (p 1)(q 1) Choose e < n such that e is relatively prime to (n). Compute d such that ed mod (n) = 1 Public key: (e, n); private key: d Encipher: c = me mod n Decipher: m = cd mod n RSA calculator: https://www.cs.drexel.edu/~jpopyack/IntroCS/HW/RSAWorkshe et.html IT 6823 LM6 Cryptography 17
Digital Signature For authentication and integrity Ensure message is from legitimate user and was not tempered Non-repudiation Implementation Hash function Public-key cryptography IT 6823 LM6 Cryptography 18
Cryptographic Hash Function One way function mapping a message to a fixed size Deterministic Quick to compute the hash value for any given message Infeasible to generate a message that yields a given hash value Infeasible to find two different messages with the same hash value a small change to a message should change the hash value so extensively IT 6823 LM6 Cryptography 19
Hash Function Example Digital signature Message authentication code Image source: https://en.wikipedia.org/wiki/Cryptographic_hash_function IT 6823 LM6 Cryptography 20
Digital Signature - PKI IT 6823 LM6 Cryptography 21
Public-Key vs. Symmetric Key Public-Key Key exchange over unsecure channel Computationally intensive Symmetric Key Higher data throughput Hybrid Cryptosystem Public-key for key exchange Symmetric key for data communication IT 6823 LM6 Cryptography 22
Kerckhoffss Principle A cryptosystem should be secure even if everything about the system, except the key, is public knowledge . Security Through Obscurity Considered Dangerous Open Discussion Encourages Better Security IT 6823 LM6 Cryptography 23
Cryptanalysis Ciphertext only attacks Known plaintext attacks Chosen plaintext attacks Chosen ciphertext attacks Man-in-the-middle attacks Side channel attacks Brute force attacks Birthday attacks IT 6823 LM6 Cryptography 24
