Modern Cryptography for Absolute Beginner

A brief introduction to the key ideas in cryptography: hashes, symmetric encryption, and asymmetric encryption, also known as public-key cryptography.

Transcript

1. Jeffrey Cohen @jeffcohen cohen.jeff@gmail.com Modern Cryptography for the absolute beginner
4. Alan Turing
6. Secret Writing Substitution Transposition Steganography Cryptography Code Cipher From "The Code Book," by Simon Singh. Doubleday, 1999
7. Cryptography is not Security
8. Cryptography There are two primary use cases for digital cryptography: • Verification • Secrecy
9. There are two uses cases for verification: • Message tampering • Authorship Cryptography
10. How can we verify that a message was transmitted perfectly without any accidental changes? Use Case: Message Tampering
11. Use Case: Parity Bits
12. C A T Content: Use Case: Parity Bits
13. 01000011 01000001 01010100 Content: Use Case: Parity Bits
14. 01000011 01000001 01010100 Even Parity: Content: 11000011 01000001 11010100 Use Case: Parity Bits
15. 01000011 01000001 01010100 Odd Parity: Content: 01000011 11000001 01010100 Use Case: Parity Bits
16. Check Digits
17. 1. Sum the digits in the odd-numbered positions, then multiply by 3. 2. Add the digits in the even-numbered positions to the previous result. 3. Divide by 10, and keep the remainder. 4. If the remainder is not 0, 
 subtract the remainder from 10. Check Digits
18. Data Verification Checksum Digest Hash Fingerprint MD5 SHA-1 SHA-256 bcrypt These are all synonyms!
19. Use Case: Password Security Password: bcrypt hash: swordfish $20A6@3AC194F02... Reversing this process is impossible.
20. Symmetric Encryption
21. Hello Symmetric Encryption
22. Hello Ifmmp "Advance by 1" Symmetric Encryption
23. Hello Ifmmp "Advance by 1" Symmetric Encryption
24. Hello Ifmmp Fortunately, this is reversible Symmetric Encryption
25. Hello Ifmmp Fortunately, this is reversible DES
 AES-256 Blowfish Symmetric Encryption
26. Hello Ifmmp But how do we transmit the key? Symmetric Encryption
27. Symmetric Encryption
28. Each key transforms data. They are called a pair because they mathematically exactly reverse the effect of the other key. Public Key Cryptography
29. One key is arbitrarily selected to be the public key, and the other will be the private key. Public Key Cryptography
30. Hello ?????? Public Key Cryptography
31. Hello x9dak Public Key Public Key Cryptography
32. Public Key Hello x9dak Private Key Public Key Cryptography
33. Mr. A Mr. B Use Case: Secret Message
34. Mr. A wants to send a secret message to Mr. B. Mr. A Mr. B Mr. B, Meet me at noon for lunch. Your friend, Mr. A Use Case: Secret Message
35. Mr. A Mr. B STEP 1: Mr. A encrypts the message with Mr. B's public key. Li%8aja^@*9cmakA P91&*C9Naxw8723h Yolq&6209CKn02K Mr. B, Meet me at noon for lunch. Your friend, Mr. A Use Case: Secret Message
36. Mr. A Mr. B STEP 2: Mr. B decrypts the message with Mr. B's private key. Li%8aja^@*9cmakA P91&*C9Naxw8723h Yolq&6209CKn02K Mr. B, Meet me at noon for lunch. Your friend, Mr. A Mr. B, Meet me at noon for lunch. Your friend, Mr. A Use Case: Secret Message
37. A1. Mr. A calculates the content's digest. A2. Mr. A encrypts the digest with his
 private key. This is the "wax seal".
 B1. Mr. B decrypts the digest value using
 Mr. A's public key. B2. Mr. B independently calculates the
 digest of the received content. B3. Mr. B expects the digests to match! Use Case: Authenticity
38. ssh-keygen -t rsa -b 4096 Wait a Minute!
39. ssh-keygen -t rsa -b 4096 Wait a Minute!
40. ssh-keygen -t rsa -b 4096 This won't work! RSA can only encrypt messages shorter than the "key length". Wait a Minute!
41. Wait a Minute! In reality, we use both! We use asymmetric cryptography to securely transmit a random symmetric key.
42. What's Next? Now: PKCS Soon: Elliptic-curve PKCS Future: Quantum implications?
43. Modern Cryptography for the absolute beginner Jeffrey Cohen @jeffcohen cohen.jeff@gmail.com