Crypto 7: Digital Signatures and Writeups
by Arnav Vora
Aside from just encrypting data, we also need a cryptographic mechanism to verify the identity of users. This is done through digital signatures. First, we discuss cryptograhic hashing functions, which act as one-way functions with the added benefit of collision resistance. Then, we discuss how we can construct a digital signature scheme using the same RSA primitives. Finally, we will have time to write writeups for challenges we have solved this quarter in cyber academy or elsewhere.
Slides
Challenges
The following challenges in increasing difficulty are deployed to platform.acmcyber.com to practice the concepts covered in the slides.
- Challenge 1 -
crypto/rubiks-cube - Challenge 2 -
crypto/prime-factory - Challenge 3 -
crypto/rubiks-cube-2 - Challenge 4 -
crypto/mitm
Resources
The following resources are great to practice/learn about the ciphers covered in the slides.
- pycryptodome: A library that implements many modern-day cryptographic algorithms.
- cryptohack: A website with many challenges related to cryptography
- Alpertron: A fast online integer factorization calculator for large numbers
- FactorDB: A large online database of integers and their factors
- DanBoneh: A paper by a Stanford professor on RSA attacks
- hackMD: A very useful markdown editor/publisher
- Twin Prime: Gary's writeup for Twin Primes from Buckeye CTF 2023, a good example of a writeup for an easier challenge.
- SHA256-CTR: Arnav's writeup for SHA256-CTR from SDCTF 2023, a good example of a writeup for a harder challenge.