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For the beginners, by a beginner
 Security Enthusiast
 Broke lock of my own bag.
 Start many things, finish nothing (mostly)
 Threat Researcher @ Symantec
 B&B
 Talking at badboy16a@gmail.com
 Broadcasting @_badbot
Functionality
Systems
 Encoding
 Encryption
 Obfuscation
 Cryptography
 Cryptanalysis
 Steganography
 Transposition
 scytale
 Substitution
 Caesar cipher
 Enigma
 Shannon’s law of secrecy
 PGP
Basics of Cryptography
Basics of Cryptography
Basics of Cryptography
Basics of Cryptography
Basics of Cryptography
Basics of Cryptography
 Messages is split in to fixed size blocks.
Block
Encryption
 Electronic CodeBook (ECB)
 Cipher Block Chaining (CBC)
 Cipher FeedBack(CFB)
 Output Feedback(OFB)
 Counter (CTR)
 Galois Counter Mode (GCM)
 Required to align data to Block length.
 Bit Padding
 Byte Padding
 Zero Padding
 ANSIx.923
 ISO-10126
 PKCS#7
 ISO/IEC 7816-4
 One way function.
 Arbitrary length input, fixed length output.
 Examples:
 CRC(16/32)
 MD(4/5)
 SHA(1/2/3/4)
 Integers
 Prime
 Co-prime
 Modulus
 Congruenc
e
 Group
 Modulus (M)
 Operation
 Identity
 Inverse
 Generator
 Ring
 Order (M-1)
iff M is
prime.
 Diffie-Hellman Key Exchange
 Alice and Bob agree to use a
modulus p = 23 and
generator g = 5.
 Alice chooses a secret
integer a = 6, then sends
Bob A = ga mod p
 A = 56 mod 23 = 8
 Bob chooses a secret
integer b = 15, then sends
Alice B = gb mod p
 B = 515 mod 23 = 19
 Alice computes s = Ba mod p
 s = 196 mod 23 = 2
 Bob computes s = Ab mod p
 s = 815 mod 23 = 2
 Alice and Bob now share a secret
(the number 2).
 Based on intractability principle
 Multiplying two large integers is easy
 Finding prime factors of large integers is an intractable problem.
 Computations are performed in “Group” modulo M.
 M being a very large prime.
 2 keys are generated simultaneously.
 Inverse of each other (modulo M).
 One encrypts (Public Key)
 Other decrypts (Private Key)
Encryption (P=5)
C = Pe
mod n 53 % 33 = 125 % 3 = 26
Decryption
P = Cd mod n 267 % 33 = 8031810176 % 33 = 5 OR
267 % 33 = 26 (3+3+1) % 33 = (263%33)* (263%33)* (26%33) = 5
Key Generation
Select 2 primes: p,q p = 11, q = 3
Calculate: n = p*q n = 33
Calculate: Φ(n) = (p-1)*(q-1) Φ(n) = 20
Choose e : gcd(e, Φ(n)) = 1, (e,n) is public key e = 3; Kpub = (3,33)
Find d : e*d = 1 mod Φ(n), (d,n) is private key d = 7, Kpriv = (7,33)
Basics of Cryptography
Basics of Cryptography
Basics of Cryptography
Basics of Cryptography
Basics of Cryptography

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Basics of Cryptography

  • 1. For the beginners, by a beginner
  • 2.  Security Enthusiast  Broke lock of my own bag.  Start many things, finish nothing (mostly)  Threat Researcher @ Symantec  B&B  Talking at badboy16a@gmail.com  Broadcasting @_badbot
  • 4.  Encoding  Encryption  Obfuscation  Cryptography  Cryptanalysis  Steganography
  • 5.  Transposition  scytale  Substitution  Caesar cipher  Enigma  Shannon’s law of secrecy  PGP
  • 12.  Messages is split in to fixed size blocks.
  • 14.  Electronic CodeBook (ECB)  Cipher Block Chaining (CBC)  Cipher FeedBack(CFB)  Output Feedback(OFB)  Counter (CTR)  Galois Counter Mode (GCM)
  • 15.  Required to align data to Block length.  Bit Padding  Byte Padding  Zero Padding  ANSIx.923  ISO-10126  PKCS#7  ISO/IEC 7816-4
  • 16.  One way function.  Arbitrary length input, fixed length output.  Examples:  CRC(16/32)  MD(4/5)  SHA(1/2/3/4)
  • 17.  Integers  Prime  Co-prime  Modulus  Congruenc e  Group  Modulus (M)  Operation  Identity  Inverse  Generator  Ring  Order (M-1) iff M is prime.
  • 18.  Diffie-Hellman Key Exchange  Alice and Bob agree to use a modulus p = 23 and generator g = 5.  Alice chooses a secret integer a = 6, then sends Bob A = ga mod p  A = 56 mod 23 = 8  Bob chooses a secret integer b = 15, then sends Alice B = gb mod p  B = 515 mod 23 = 19  Alice computes s = Ba mod p  s = 196 mod 23 = 2  Bob computes s = Ab mod p  s = 815 mod 23 = 2  Alice and Bob now share a secret (the number 2).
  • 19.  Based on intractability principle  Multiplying two large integers is easy  Finding prime factors of large integers is an intractable problem.  Computations are performed in “Group” modulo M.  M being a very large prime.  2 keys are generated simultaneously.  Inverse of each other (modulo M).  One encrypts (Public Key)  Other decrypts (Private Key)
  • 20. Encryption (P=5) C = Pe mod n 53 % 33 = 125 % 3 = 26 Decryption P = Cd mod n 267 % 33 = 8031810176 % 33 = 5 OR 267 % 33 = 26 (3+3+1) % 33 = (263%33)* (263%33)* (26%33) = 5 Key Generation Select 2 primes: p,q p = 11, q = 3 Calculate: n = p*q n = 33 Calculate: Φ(n) = (p-1)*(q-1) Φ(n) = 20 Choose e : gcd(e, Φ(n)) = 1, (e,n) is public key e = 3; Kpub = (3,33) Find d : e*d = 1 mod Φ(n), (d,n) is private key d = 7, Kpriv = (7,33)

Hinweis der Redaktion

  1. PGP Later
  2. https://www.digicert.com/images/iot/IoTSecuritySolutionGraphic_400x400.png
  3. DES: by IBM, Lucifer, NSA? Why not 2DES? Meet-in-the-middle
  4. Symmetric key must be shared before use.
  5. Encrypts one bit/byte. Perfect: One Time Pad
  6. Linear Feedback Shift Register Designed to be implemented in H/W (A5/1), CSS Initial State, Key, Tap Points
  7. DES Block size: 64 bits, Keysize: 56b (+8b parity) AES Block Size: 64 bits, Key size: 64, 128, 256
  8. GCM provides authentication also.
  9. Must be identifiable after decryption Ciphertext Stealing
  10. SHAttered Fuzzy hashing.
  11. Primality Test Multiplicative Group
  12. Multiplicative group
  13. RSA?? Extended Euclid,s Algorithm e is small, usually 65537.
  14. Trust = Sign their public key.
  15. The Irony