Diffie-Hellman Key Exchange explained

This topic is to discuss the following lesson:


I have trouble viewing this video.
It says: No palyable sources found. Please advise

Just fixed it, it’s working again.


In configuring an ISAKMP Policy, Phase-1, one of the negotiable attributes in the policy is the Diffie-Hellman Group x. Where x is a number. What does the x (number) represent?


Hi Joey,

It’s the DH group number which basically is the strength of the key that we use in the DH key exchange. Higher group numbers are more secure but take longer to calculate:

DH Group 1: 768-bit group
DH Group 2: 1024-bit group
DH Group 5: 1536-bit group
DH Group 14: 2048-bit group
DH Group 15: 3072-bit group
DH Group 19: 256-bit elliptic curve group
DH Group 20: 384-bit elliptic curve group



Long time since I posted. This is a wonderful video thanks for sharing. I understand it conceptually but what do the red and green locks represent. I understand that the blue key is basically the shared key that will be used to encrypt data in transit.

Hi Michael,

Take a look at this video (start from 2:39):

It explains the same process but with the math, I think that will be helpful.