Question about IPSEC

[Abdelilah Benrida]

Is it true that ipsec use RSA algorithm when we use the pre-shared Key?

[Karsten Iwen]

No, there aren't any public-key-operations involved in the authentication when you use PSKs. The only public-key-operation is DH for the Key-agreement.

Where did you get that info from?

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[Abdelilah Benrida]

i read that IKE phase one  for IPSEC uses the asymetric cryptography and the second uses the symetric one.

should i understand that with pre-shared key there is no asymetric cryptography in IKE phase 1?

[Karsten Iwen · Accepted solution]

i read that IKE phase one  for IPSEC uses the asymetric cryptography and the second uses the symetric one.

both can be the case but as a general rule it's not correct.

should i understand that with pre-shared key there is no asymetric cryptography in IKE phase 1?

yes and no ... 😉

You always have the Key-Agreement with Diffie-Hellman which is also an asymetric mechanism. That takes place both with PSK and digital certificates (rsa-sig).

For authentication - and that's probably what you are referring to - with PSKs there is no public-key operation but a couple of hash-operations.If you authenticate with digital certificates you have plenty of public-key operations where digital signatures are computed and also checked.

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[Abdelilah Benrida]

Ok thank you very much