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expand on hybrid concept

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Tammi L. Coles 2023-10-13 17:43:09 +02:00 committed by Heiko Schaefer
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@ -128,7 +128,10 @@ Digital signatures in OpenPGP are used in two primary contexts:
(hybrid_cryptosystems)=
## Hybrid cryptosystems
[Hybrid cryptosystems](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) merge the strengths of two distinct cryptosystems, capitalizing on their respective advantages:
OpenPGP uses a hybrid cryptosystem. [Hybrid cryptosystems](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) combine the use of symmetric and asymmetric (public-key) cryptography to capitalize on the strengths of each.
- Public-key cryptosystem: used to securely exchange shared secrets, known as "session keys" in OpenPGP, across insecure channels
- Symmetric-key cryptosystem: used to efficiently encrypt and decrypt long messages, leveraging an OpenPGP "session key" as the shared secret
Within OpenPGP's hybrid system, so-called "session keys" are central. They are generated uniquely for each session and are instrumental in both encrypting and decrypting the actual message content, using the efficiency of symmetric-key cryptography.
Using asymmetric (public-key) cryptography, the session keys are also encrypted. This ensures that only the intended recipient, the holder of the corresponding private key, can decrypt and gain access to the session key. With the decrypted session key, they can then use the session key to decrypt the actual message.
OpenPGP's dual-layered security thus capitalizes on symmetric cryptography's speed and efficiency and asymmetric (public-key) cryptography's mechanism for secure key exchange.