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Symmetric encryption algorithms are known to be fast but present great challenges on the key management side. Asymmetric encryption algorithms are slow but allow communication with a remote host without having to transfer a key out of band or in person. If we combine the strength of both crypto systems where we use the symmetric algorithm to encrypt the bulk of the data and then use the asymmetric encryption system to encrypt the symmetric key, what would this type of usage be known as?
Because of the complexity of the underlying problems, most public-key algorithms involve operations such as modular multiplication and exponentiation, which are much more computationally expensive than the techniques used in most block ciphers, especially with typical key sizes. As a result, public-key cryptosystems are commonly 'hybrid' systems, in which a fast symmetric-key encryption algorithm is used for the message itself, while the relevant symmetric key is sent with the message, but encrypted using a public-key algorithm. Similarly, hybrid signature schemes are often used, in which a cryptographic hash function is computed, and only the resulting hash is digitally signed.