A hybrid cryptosystem merges the advantages of public-key and symmetric-key cryptography. Public-key systems offer convenient secure communication without requiring a shared secret, but they can be resource-intensive. Symmetric-key systems are more efficient but require a shared secret. Hybrid systems mitigate their downsides by combining both approaches. They typically use symmetric-key cryptography to encrypt the bulk of the data and public-key cryptography to securely exchange the symmetric keys.