7.11 Hybrid cryptosystems
From the previous sections, you might have got the (correct) impression that using a public-key cryptosystem is rather costly in terms of computation time. For example, according to [177], p. 121 key generation in the RSA cryptosystem has an effort in O(ℓ4 log(ℓ)), where ℓ is the bitlength of the public modulus n, and encryption or decryption of an n-bit plaintext block takes O(n3 bit operations. Such an effort is unacceptable for the encryption of large amounts of data.
Therefore, most cryptographic systems used in practice today are hybrid cryptosystems. Hybrid cryptosystems combine the advantage of public-key cryptography of being able to bootstrap a secure communication channel to a previously unknown communicating party with the speed and efficiency of symmetric-key encryption, decryption, and hashing operations [188].
7.11.1 High-level description of hybrid cryptosystems
Figure 7.6 illustrates the basic architecture...
