[PROPOSAL] Hybrid Cryptosystem Proposal - DHKE + AES

[robertDurst]

AFAIK, RSA isn't supposed to be used as a message encryption system. Instead, it (asymmetric) is better when combined with a symmetric system, forming a hybrid cryptosystem.

As defined by Wikipedia:

A hybrid cryptosystem can be constructed using any two separate cryptosystems:

• a key encapsulation scheme, which is a public-key cryptosystem, and
• a data encapsulation scheme, which is a symmetric-key cryptosystem.

Hybrid Cryptosystem Proposal

I propose we move away from RSA and instead use the following scheme:

1. Alice, Bob, and Charlie agree on a finite, cyclical group G of order n with generator g and modulo p.
2. Alice, Bob, and Carol each generate a random natural number a, b, and c respectively such that they are greater than 0 and less than n
3. Alice, Bob, and Carol join the server, registering their public keys g^a and the server broadcasts these public keys to all participants.
4. Alice wants to send a message to Bob, so she calculates (g^b)^a.
5. Alice utilizes AES with (g^b)^a as the secret key to encrypt message m -> c_b.
6. Alice broadcasts [BOB_PUBLIC_KEY][ALICE_PUBLIC_KEY]: c_b.
7. Bob receives Alice's message, calculates (g^a)^b and decrypts c_b.

References:

• Hybrid Cryptosystem
• Diffie-Hellman
• AES
• RSA vs. DH