Diffie-hellman groups to avoid

1. Which DH groups to avoid?
2. What is the difference between DH Group 14 and 5?
3. What is Diffie-Hellman Group 20?

Which DH groups to avoid?

DH (Diffie-Hellman) algorithms, used for key exchange, should not be used for groups with a bit value of 1024 or less.

What is the difference between DH Group 14 and 5?

DH with 1536 bits (group 5) has 89 bits of security. DH with 2048 bits (group 14) has 103 bits of security.

What is Diffie-Hellman Group 20?

Group 20 = 384-bit EC = 192 bits of security

That is, both groups offer a higher security level than the Diffie-Hellman groups 14 (103 bits) or 5 (89 bits).