Hybrid Cryptosystem

Hybrid Cryptosystem

In cryptography, public-key cryptosystems are convenient in that they do not require the sender and receiver to share a common secret in order to communicate securely (among other useful properties). However, they often rely on complicated mathematical computations and are thus generally much more inefficient than comparable symmetric-key cryptosystems. In many applications, the high cost of encrypting long messages in a public-key cryptosystem can be prohibitive. A hybrid cryptosystem is one which combines the convenience of a public-key cryptosystem with the efficiency of a symmetric-key cryptosystem.

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.

The hybrid cryptosystem is itself a public-key system, whose public and private keys are the same as in the key encapsulation scheme.

Note that for very long messages the bulk of the work in encryption/decryption is done by the more efficient symmetric-key scheme, while the inefficient public-key scheme is used only to encrypt/decrypt a short key value.

Read more about Hybrid CryptosystemExample, Security

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... chosen ciphertext attacks, then the hybrid scheme inherits that property as well ... However, it is possible to construct a hybrid scheme secure against adaptive chosen ciphertext attack even if the key encapsulation has a slightly weakened ...