Issue # 17: Diffie-Hellman, Github SSH Accounts, UR(L/I/N)

Hey Hey 👋

What a week, huh? Too many things happening both personally and around the world, while at the same time trying to figure out German healthcare system and how it will fit into my upcoming freelancing journey.

Turns out, German healthcare system is tooooo expensive and costs a lot of money. There are many horror stories especially from migrants about how inadequate the service can be. But this story is for another day.

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In This Issue

• News & Articles: Tech Compensation, 23andMe Bankruptcy, Lieferando Layoffs, Zalando’s scandal, EU Open Source Catalogue

• Poll: Interested into Self-employment?

• Weekly Summary:

  • Diffie-Hellman Key Exchange

  • Multiple Github SSH Accounts

  • URL vs URI vs URN

• Weekly Videos

  • How to Start a SOLO Agency Step-By-Step

  • World's shortest UI/UX design course

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News & Articles

• Trimodal Nature of Tech Compensation in the US, UK and India

• DNA of 15 Million People for Sale in 23andMe Bankruptcy

• Lieferando couriers fear massive cuts

• Court Rules Against Zalando for Racist, Unlawful Dismissal

• The EU Open Source Solutions Catalogue is now live

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Poll

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This week’s Summaries

Diffie-Hellman Key Exchange

Diffie-Hellman Key Exchange is a method to securely exchange cryptographic keys over a public channel. It uses a mix of asymmetric and symmetric encryption to create a secure channel.

We have three parties: Client, Server, and Attacker.

The steps are:

1. The client and server agree on two numbers: a prime number, and a base number.

2. The client and server generate a private key and a public key.

3. The client and server exchange their public keys which has the following formula: public_key = (base_number ^ private_key) % prime_number.

4. They then exchange the public keys and generate a shared secret key using the following formula: shared_secret_key = (public key of the other party ^ private key) % prime_number.

5. Doing this, mathematically, the shared secret key will be the same for both the client and server.

6. The client and server can now communicate securely using the shared secret key.

Diffie-Hellman protects against Forward Secrecy, which means that if the attacker gets the private key, they can't decrypt the previous messages.

Protecting against Forward Secrecy is important because if the attacker gets the private key, they can decrypt all the previous messages. With Diffie-Hellman, the attacker can't decrypt the previous messages because the shared secret key is only used for the current session and every session has a different shared secret key.

Read more:

• Explaining the Diffie-Hellman Key Exchange

• Secret Key Exchange (Diffie-Hellman) - Computerphile

• Diffie Hellman -the Mathematics bit- Computerphile

• Perfect Forward Secrecy

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Multiple Github SSH Accounts

This is useful when you have multiple accounts for github or any other git repo provider on the same machine (ex: Work and Personal accounts).

The concept is that we need to:

• Generate different SSH keys for each account

• Add ssh keys to ~/.ssh/config with separate hosts

• Add condition to .gitconfig to use certain user for a certain directory for example

• We pull the repo using a specific host name (not the domain)

Steps:

1. Generate SSH keys:

ssh-keygen -t ed25519 -C "<email_address>"

1. Add the keys to ~/.ssh/config:

Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_ed25519

Host github.com-personal
    HostName github.com
    User git
    IdentityFile ~/.ssh/id_ed25519_personal

1. Add the condition to .gitconfig:

[includeIf "gitdir:~/work/"]
  path = .gitconfig-work

Then create a .gitconfig-work file with the following content:

[user]
  email = <email_address>
  name = <name>
[core]
    sshCommand = "ssh -i /path/to/work/ssh/file -o IdentitiesOnly=yes"

1. Clone the repo using the specific host:

git clone git@github.com:repo_org/repo_name.git

For the personal account:

git clone git@github.com-personal:repo_org/repo_name.git

and afterwards, you can use git commands normally and it will know which credentials to use.

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URL vs URI vs URN

This topic might be very technical but it explains the different names and what are the different parts used to find a resource on the internet.

Let's take the following:

https://john.doe@www.example.com:123/form/questions/?tag=networking&order=news#top

It consists of:

• https: Scheme. This can be HTTP, HTTPS, FTP, MAILTO, IRC, FILE, etc

• john.doe: Userinfo

• www.example.com: host

• 123: Port

• john.doe@www.example.com:123: Authority

• /form/questions: Path

• ?tag=networking&order=news: Query

• #top: fragment

This full thing is called a Universal Resource Locator (URL). It's used to locate exactly where is the resource.

Meanwhile, Universal Resource Identifier (URI) is used to uniquely identify a resource but not necessarily how to locate it. So, URL is just a URN + Scheme (how to locate a resource)

Uniform Resource Name (URN) are names like URI but they should be unique across space and time. They are more regulated and they usually start with the prefix urn:.

Read more:

• The Real Difference Between a URL and a URI

• What is the difference between a URI, a URL, and a URN?

• Why is URN one of more popular formats used to uniquely identify the resource?

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Videos of the Week

How to Start a SOLO Agency Step-By-Step

World's shortest UI/UX design course

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