How is encryption key generated in router with encryption aes configured??

Question

Recently I was doing IPsec configuration in gns3 using encryption-aes , hash-sha & authentication-preshare key BUT what I'm confused is there is always an encryption key to encrypt the data, isn't it??? If it is then how does router with IPsec generates encryption key & if this key encrypts the data then what exactly 'aes' does??? Also how to know whether the key is symmetric key (private) or asymmetric key (public) ??? Can anyone plzz!!! explain this to me in an easiest way? thanx

Answer 1

The key word here is "pre-shared key". This obviously requires that both parties agree on a key, which is shared pre (before) the encryption.



A common example is a VPN tunnel, where both parties agree on the used encryption algorithms and a common password/key and set up both ends accordingly.



I assume the encryption key is generated based on the pre-shared key; I'm not sure why that matters though; you don't need to know how exactly AES works in order to use it.

Answer 2

The pre-shared key is shared using public key cryptography e.g RSA or Diffie-Hellman. This pre-shared key is then used in the AES symmetric encryption.

Answer 3

AES read here https://en.wikipedia.org/wiki/Advanced_Encryption_Standard