0 sats \ 4 replies \ @ek 20 Jan 2023 \ parent \ on: emon: encrypted messaging over nostr with lightning integration ⚡ nostr
Yes, you are right, they need it for decryption. The IV is available since it's appended as a query parameter.
How the recipient is able to derive the same key is a good question though. The key seems to be derived using elliptic curves. Will check how this works. They use this library: https://github.com/paulmillr/noble-secp256k1
https://medium.com/asecuritysite-when-bob-met-alice/a-bluffers-guide-to-secp256k1-404e423e612
The main applications of secp256k1 are in digital signing (ECDSA) and key exchange (ECDH)
ECDH with secp256k1 can apparently be used to generate a shared key which is then used in the AES cipher. I'm continuing this rabbit hole though because my mind is getting blown to bits:
https://asecuritysite.com/ecdh
You guys gotta learn this with me. This is nuts if true. If the participants really can't find each other's private keys after this exchange.
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Will learn this with you when I have more time. I am on mobile atm and switching tabs and stuff gets really annoying haha
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Nooo because in order for this to work,
"Bob will generate a public key (B) and private key (b), as will Alice (A and a). They then exchange their public keys, and the shared key will then be a×b×G, and where G is the generator point on the elliptic curve."
https://www.youtube.com/watch?v=aQ9pZ6wVV_E
Okay so Bob sends bG to Alice and Alice sends aG to bob, but then that means Alice can do result/G = b and Bob can do result/G = a and then on NOSTR start posting notes as each other's identities...right?
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No. I haven't watched your video but Computerphile made a very good video about diffie hellman: https://youtu.be/NmM9HA2MQGI
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