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The Basics of Cryptography

Tomasz Waszczyk
September 18th, 2022 · 1 min read

…seems like life gave me a call to action…

Introduction

Every time you connect to the Internet, you are likely to be using elliptic curves to generate the encryption key that you and the server are using. This is a unique key, and that builds on the Diffie-Hellman method, but uses the beauty of elliptic curves.

Diffie-Hellman

Creation of Bitcoin address from scratch

In order to create a Bitcoin address, a private key, which is a randomly generated number, is multiplied using an elliptic curve to produce a publik key. Generated public key is then put through both SHA-256 and RIPEMD-160 hashing algorithms.

1A = RIPEMD-160( SHA-256(K) )
2
3where
4
5A - Encrypted public key
6K - Public key

The use of the SHA-256 and RIPEMD-160 hashing algorithms for the creation of a Bitcoin address gave one big advantage: shorter addresses. A public key is 256 bits long whereas, the hashed version of the Bitcoin address is 160 bits long.

As we can see, the SHA-256 hashing algorithm is a core part of the Bitcoin protocol, but it is not enough. Using additionally RIPEMD-160 is like psychopath vibe - so needed in this kind of systems.

The. World. Is. Crazy. LITERALLY.

But only the truth is interesting.


Software engineering versus cryptographers

Cryptography

Random fact 1: The inventor of SHA-2 (Secure Hash Algorithm 2) is United States National Security Agency (NSA), their work was published publicly in 2001.

Random fact 2: NSA advises dropping C/C++ and moving to memory-safe languages. It’s something that large industry players were saying a long time ago. Nevertheless, it’s good to see NSA supporting the idea.

NSA

PS. In the header of the post is a picture of Marian Rejewski - the great Polish code breaker, the author of bombe decryption machine built in Bletchley Park. Marian Rejewski together with Jerzy Różycki and Henryk Zygalski developed techniques to decrypt the German machine ciphers during World War II.

If you really want to get down in the weeds

  1. One time pad
  2. Wallet from private key
  3. Cryptohack Challenges
  4. Cryptopals
  5. NSA urges orgs to use memory-safe programming languages
  6. A Graduate Course in Applied Cryptography

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