Intro to Cryptography Definitions Cryptography Cryptanalysis - - PowerPoint PPT Presentation

▶
intro to cryptography definitions
SMART_READER_LITE
LIVE PREVIEW

Intro to Cryptography Definitions Cryptography Cryptanalysis - - PowerPoint PPT Presentation

Sep 09, 2022 220 likes •384 views

Intro to Cryptography Definitions Cryptography Cryptanalysis Cryptology CRYPTOGRAPHY Plaintext Cyphertext More definitions block cipher stream cipher hash function shared key public key digital signature

slide-1
SLIDE 1

Intro to Cryptography

slide-2
SLIDE 2

Definitions

  • Cryptography
  • Cryptanalysis
  • Cryptology
slide-3
SLIDE 3

Plaintext Cyphertext

CRYPTOGRAPHY

slide-4
SLIDE 4

More definitions

  • block cipher
  • stream cipher
  • hash function
  • shared key
  • public key
  • digital signature scheme
slide-5
SLIDE 5

Caesar Cipher

  • Rotate all letters by a fixed amount.
  • Htruzyjw xhnjshj nx fbjxtrj
slide-6
SLIDE 6

Vigenère Cipher

  • Fixed short pad
  • Plain: tobeornottobethatisthequestion
  • Key: runrunrunrunrunrunrunrunrunrun
  • KIOVIEEIGKIOVNURNVJNUVKHVMGZIA
slide-7
SLIDE 7

Playfair Cipher

P A L M E R S T O N B C D F G H I K Q U V W X Y Z

lo rd gr an vi lx le sl et te rz

MT TB BN ES WH TL MP TA LN NL NV

slide-8
SLIDE 8

Exercises

  • Caesar Cipher: Zgo dgfy vg qgm osfl lzwkw

ewkksywk lg jwesaf kwujwl

  • Vigenère: Encrypt “Computer science is fun” with

“secure”

  • Playfair: Same as above
slide-9
SLIDE 9

One Time Pad

  • Provably perfectly secret
  • Pad as long as plaintext
  • Pad perfectly random
  • Pad only used precisely once
  • Red Phone
slide-10
SLIDE 10

One-Way Function

  • Given the output, you cannot compute the input in

polynomial time.

Plaintext Cyphertext

One-way Function

Cyphertext Plaintext

slide-11
SLIDE 11

One-Way Functions

  • Password hashing
  • Code books
  • others?
slide-12
SLIDE 12

Public Key Crypto

Mailbox

Letter

slide-13
SLIDE 13

Public Key Crypto

Plaintext Cyphertext

What if only one person could decipher all the cipher texts?

slide-14
SLIDE 14

Public Key Crypto

  • Each person has a key pair
  • public key — published for all the world to see
  • private key — decrypts messages
  • Anyone can encrypt a message with a public key
  • Only the owner can decrypt messages
slide-15
SLIDE 15

Digital Signatures

  • Sign a message with a private key
  • Anybody can verify with my public key
  • Public key widely published
slide-16
SLIDE 16

Issues

  • How do we know if a cypher is “good”?
  • How do we avoid usability weaknesses?
  • Do we plan on using existing devices in our

scheme?

  • How to we model adversarial behaviors?
  • How do we verify that our adversaries are covered?