Double ratchet algorithm: The ping-pong game encrypting Signal and WhatsApp

How do text messaging services like Signal and WhatsApp keep your text messages secure? The Double Ratchet algorithm.

Let’s say Alice wants to send Bob an end-to-end encrypted message. She uses a key to lock up the message and Bob uses the same key to unlock the message. But what if they want to send a bunch of messages back and forth? Using the same key the whole time is not very secure. It would be better to have a unique key for each message. The Double Ratchet algorithm cranks out a new key each time you send a message by combining a key derivation function and a Diffie-Hellman calculation.

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Created by Kelsey Houston-Edwards

[Harkunwar]

I’m so surprised this channel just came in my recommendation now. When you hosted Infinite Series it was my favourite channel and I still go back to those videos. So happy to have discovered you again.

[erickaguirre]

How are these videos under 1k views? This is the best explanation I've seen in YouTube about this topic

[shallanrambaran]

It is very rare that I find someone so good at explaining something complex expecially on YouTube. I am going to subscribe.

[seven.]

Used to watch infinite series and was sad to see it go, so glad you have your own channel! You are a fantastic maths communicator. I've liked, subscribed and recommended your videos!

[iamdigory]

So glad you are back on YouTube! Your infinite series videos are in the very top tier of math education. There are very few people that can teach math as well as you can.

[TenderBug]

Wow such a surprise. Great to learn from you after long time.

[Jonas-Seiler]

I don’t really understand what the benefit of the additional key derivation function is if they generate new asymmetric key pairs for every message either way. Like it seems to me wether they use that additional function or not, an attacker would have to do the exact same thing.

[delphine]

this is hands down the best explanation I've come across. thank you sm

[Cookiekeks]

This is probably the best explanation I've seen for any topic, ever.

[pablorackham]

Funny that the video is sponsored by Wire but doesn't mention how Wire does its encryption ^^.

Great video though, and great channel! I just discovered it with the lattice encryption video which was also excellent. I'll add it to my list of recommended channels, and send it to my students! Thanks!

[NomadicVoxel]

Huhhh, two year old video, how'd it get into my feed? Excited to see it though, I loved that other show she ran, Infinite Series.

[gx]

8:42 how do you verify that the new public keys are associated with the desired person and not a man-in-the-middle?

[topherjaynes]

This was so helpful, thanks for taking the time to make this very understandable.

[davenddominick]

this explanation was incredibly clear. Thank you

[conroybogle]

Great video! You're so pleasant to listen to, and concise

[harshadevapriyankarabandar]

This channel is very helpful.thank you

[yapayzeka]

8:43 I dont understand something. Alice lost her first priv/pub key pair after response. how can she decrypt previous messages?

[ehasaranga]

Really thankful for this explaination ❤️

[mrdevops]

I guess an understanding of Diffie-Hellman would be a helpful pre-req here.

[cbrunnkvist]

Wow, this channel is on par with @Computerphile. Subbed! 🎉