a quick tour of cryptographic primitives n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
A Quick Tour of Cryptographic Primitives PowerPoint Presentation
Download Presentation
A Quick Tour of Cryptographic Primitives

Loading in 2 Seconds...

play fullscreen
1 / 8

A Quick Tour of Cryptographic Primitives - PowerPoint PPT Presentation


  • 172 Views
  • Uploaded on

18739A: Foundations of Security and Privacy . A Quick Tour of Cryptographic Primitives. Anupam Datta CMU Fall 2009. Basic Cryptographic Concepts. Encryption scheme (symmetric and public key) Signature scheme Message authentication code Hash function

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'A Quick Tour of Cryptographic Primitives' - booker


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
basic cryptographic concepts
Basic Cryptographic Concepts
  • Encryption scheme (symmetric and public key)
  • Signature scheme
  • Message authentication code
  • Hash function
  • A network protocol like SSL is built using these primitives
symmetric encryption scheme
Symmetric Encryption Scheme
  • Key generation algorithm
    • Produces a key that is used for encryption and decryption
  • Algorithm to encrypt a message
  • Algorithm to decrypt a ciphertext
  • Correctness:
    • Decrypting a ciphertext obtained by encrypting message m with the corresponding key k returns m

dec(enc(m,k),k) = m

  • (Symbolic) Security:
    • A ciphertext cannot be decrypted without access to the key

Can you think of a stronger security property?

public key encryption scheme
Public-Key Encryption Scheme
  • Key generation algorithm
    • Produces private decryption & public encryption key pair
  • Algorithm to encrypt a message
  • Algorithm to decrypt a ciphertext
  • Correctness:
    • Decrypting a ciphertext obtained by encrypting message m with the corresponding encrytion key returns m

dec(enc(m, pk(A)), sk(A)) = m

  • (Symbolic) Security:
    • A ciphertext cannot be decrypted without access to the private decryption key

Why would you want public key encryption?

signature scheme
Signature Scheme
  • Key generation algorithm
    • Produces private signing & public verification key pair
  • Algorithm to sign data
  • Algorithm to verify signature
  • Correctness:
    • Message signed with a signing key verifies with the corresponding verification key

verify(m,sign(m,sk(A)), pk(A)) = ok

  • Security:
    • A signature cannot be produced without access to the private signing key

Can you think of a scenario where you may not want non-repudiation?

message authentication code mac
Message Authentication Code (MAC)
  • Key generation algorithm
    • Produces a key
  • Algorithm to mac a message
  • Algorithm to verify a mac on a message
  • Correctness:
    • Message mac-ed with key verifies with the same key

verify(k, m, mac(k,m)) = ok

  • Security:
    • A MAC cannot be produced without access to the key

Similar to signature, but uses symmetric key

What property does a signature have, but a MAC does not?

hash functions
Hash Functions
  • Key generation algorithm
    • Produces a key
  • Algorithm to hash a message m, given a key k to a fixed length output hash(k, m)
  • Security (Collision resistance)

Given hash function hash: X  Y and key k, cannot find a

collision, i.e. x, x’  X s.t. x ≠ x’ and hash(k,x) = hash(k,x’)

What is the difference between a MAC and a hash function?

cryptographic constructions
Cryptographic Constructions
  • Signature scheme
    • DSS, RSA-FDH,…
  • Hash function
    • SHA-1, MD5,…
  • Message Authentication Code (MAC)
    • HMAC, CBC-MAC, NBAC…
  • Encryption scheme
    • Asymmetric (public key): RSA, Diffie-Hellman, El Gamal,… (distinct keys for encryption and decryption)
    • Symmetric: DES, 3DES, AES, RC4,… (same key for encryption and decryption)
  • Want to know more?
  • 18-733: Applied Cryptography

Later: Peeking inside the RSA encryption scheme