2.5.3. Comparative analysis of symmetric and asymmetric encryption algorithms

The main disadvantage of symmetric encryption is the need to transfer keys "from hand to hand" (via a secret communication channel), which is not always achievable in practice. This disadvantage is very serious, since it makes impossible the use of symmetric encryption in systems with an unlimited number of participants. However, asymmetric encryption algorithms have many more disadvantages. The first one is the low speed of encryption and decryption operations, due to the presence of resource-intensive operations. The encryption / decryption time of asymmetric algorithms is, on average, three orders of magnitude longer than the symmetric one in cryptographic strength.

Another flaw is theoretical. As already mentioned, mathematically, the cryptographic strength of asymmetric encryption algorithms has not been proven - it has not yet been possible to prove that its solution is impossible in a reasonable time.

The need to protect public keys from spoofing creates unnecessary difficulties - by replacing the legal user’s public key, an attacker will be able to encrypt an important message with his public key and later easily decrypt it with his secret key. This requires additional measures to organize the encryption protocol, for example, the use of certification of the public keys of participants.

However, these disadvantages do not prevent the widespread use of asymmetric encryption algorithms. Today there are cryptosystems that support certification of public keys, as well as combining symmetric and asymmetric encryption algorithms, when, for example, information is encoded with a symmetric encryption key, and the secret key is encoded with an asymmetric scheme.