Image for post
Image for post
Image source: Jon Moore Unsplash

Part 1 of an 8-week explainer series based on Dan Boneh’s Crypto I

I hope this serves as a practical, easy-to-understand guide for crypto enthusiasts who want a stronger understanding of ciphers, encryption, number theory, and public-key encryption methods. No coding/math skills required.

This week we cover:

  • Basic symmetric ciphers: OTPs, stream ciphers
  • Security definitions: perfect secrecy, semantic security

Understanding Basic Ciphers

Cryptographic ciphers are algorithms that scramble your secret messages, e.g. into nonsensical, random-looking text, called ciphertext.

To the casual observer, the ciphertext alone doesn’t mean anything. Thus if it is leaked, your secret is still preserved. For example, this ciphertext has no standalone meaning.

A cryptographic cipher can be as simple as an alphabetical substitution:

Image for post
Image for post
An example of a (very insecure) Substitution Cipher

Based on the above Substitution Cipher, what does the following encrypted ciphertext say? …

Image for post
Image for post

And how Polkadot & Substrate fits into this ecosystem

I recently gave a talk at Cogx about how blockchains scale. Where, we also discoursed how Polkadot fits into a future ecosystem where many blockchains are operating at scale.

In the same vein, this post relays:

  • A brief history of blockchain scaling solutions
  • Polkadot & Substrate’s role in this ecosystem
  • Polkadot & Substrate’s layer 1 and 2 scaling solutions

Note: Many better articles have previously addressed blockchains scaling issues. If this topic is foreign, I suggest reading the Crypto Canon’s scaling primers here.

Note: My views in this post do not represent that of the company which employs me. …

Image for post
Image for post

This is a somewhat illustrated guide to Zero Knowledge

I recently listened to this ZKFM podcast, which gave practical examples that clearly explained key concepts in zero knowledge. I felt inspired to transcribe them here.

In cryptography, zero knowledge proofs let you convince me that you know something, or have done something, without revealing to me what your secret thing was.

Image for post
Image for post

Practically, zero-knowledge is important because it gives you privacy in situations where you’d otherwise have to reveal confidential information. Examples include:

  • Logging into a website: rather than typing your password into a potentially unsafe website, you can simply send a proof that you “know your password”.
  • Authenticating your identity: rather than giving your mother’s maiden name over the phone to a random, bank call center agent, you can simply send a proof (a cryptographic fingerprint), that you are who you say you are. …


Nicole Zhu

Engineer @ParityTech | I write about cryptography and code | Tweet @nczhu

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store