HMAC to authenticate the source IKE-2

HMAC: Hash-based Message Authentication Code or Hash-based MAC

MAC # signature or cryptographic checksum

>>> the message has not been changed

Stream cypher ( Block ) are very quick, good for streaming traffic, mobile traffic.

MAC	https://www.youtube.com/watch?v=DiLPn_ldAAQ&ab_channel=IntroductiontoCryptographybyChristofPaar
	symmetrical key ( how to exchange/distribute/change keys )
1	Arbitrary Input length
2	Fix output length
3	message authentication: because of the secure channel use - build with private/public Key
4	Integrity ( change inline )
5	None-repudiation is not given ( the Rx can create from the message the signature with the symmetrical key)

HMAC ( Nested MAC(MAC(message) )	Integrity and Authentication
2 stage Hashing ( XOR ) with 2 different key ( ipad and opad )	https://www.youtube.com/watch?v=wlSG3pEiQdc&ab_channel=Computerphile inner key / outer key Keys are 510bits ( fixed value, in the standard ) ipad: opad: HMAX(message) = h [ (K"+opad) \|\| ( h(K"+ipad)\|\|x) ]
Sender ( Data + pre-shared Key ) > hash>> HASH1 send: Data + Hash1	Receiver: ( Data + preshared key) Data > hash> Hash2 Compare Hash2 wit rx Hash1
Usage of HMAC
	IKE Phase 2 (in IPSEC VPN)
	TLS (old name SSL) for website using HTTPS TLS replace the good old SSL / Secure Socket Layer control protocol TCP/443