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I've been tasked with building a Web Assembly site that implements E2EE. I was thinking of using ElGamal Encryption to encrypt the message and Diffie-Hellman to establish the key. After doing further research, I'm having trouble understanding the practical use cases of using ElGamal vs Diffie-Hellman.

If I'm understanding correctly. Diffie-Hellman and ElGamal both rely on the discrete log problem which makes them both ideal. Diffie-Hellman only establishes a key between two hosts, then a symmetric cryptography system is used to send a message. ElGamal encrypts the message one time, using the same method as Diffie-Hellman and then it must be regenerated each time which is slow and time consuming. So I'm thinking Diffie-Hellman would be best for a scenario when users are communicating frequently, and ElGamal for a one time file transfer.

So I am debating on which use within my web app. I was initially thinking to use both Diffie-Hellman and ElGamal. Now, I am thinking to use Diffie-Hellman to establish a key between two parties, then use a symmetric encryption scheme like AES.

One article I found particularly useful was https://www.commonlounge.com/discussion/2be4d294aa9e44d4b67f6644cd9b5ced

Particularly, Heading "Practical use and Applications"

If I were to use Diffie-Hellman & AES, how often would a key need to be regenerated?

I'm hoping someone can confirm if I'm understanding the practical uses correctly and help fill in any gaps in my understanding.

Thank you!

Davis
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2 Answers2

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You probably want authenticated/hybrid encryption and there's probably high level functions in whatever crypto library you're using.

Here's another question where they're using IES in BouncyCastle:

https://stackoverflow.com/questions/33297274/using-bouncycastle-to-encrypt-with-ecies-in-java

Grifball
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in ElGamal you use an additional variable K which is different for each message. you don't run the algorithm from scratch again for every new message.

M.Hamza Ali
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