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Cisco ASA AnyConnect VPN Using Certificate Bit Size Support

Hi,

I am new to asa and i am trying to understand the maximum key-pair size that is support for ssl vpn? Based on http://www.cisco.com/en/US/docs/security/asa/asa83/asdm63/configuration_guide/access_certs.html ,  

Key pairs are RSA keys, which have the following characteristics:

RSA keys can be used for SSH or SSL.

SCEP enrollment supports the certification of RSA keys.

For the purposes of generating keys, the maximum key modulus for RSA keys is 2048 bits. The default size is 1024. Many SSL connections using identity certificates with RSA key pairs that exceed 1024 bits can cause a high CPU usage on the adaptive security appliance and rejected clientless logins.

For signature operations, the supported maximum key size is 4096 bits.

You can generate a general purpose RSA key pair, used for both signing and encryption, or you can generate separate RSA key pairs for each purpose. Separate signing and encryption keys help to reduce exposure of the keys, because SSL uses a key for encryption but not signing. However, IKE uses a key for signing but not encryption. By using separate keys for each, exposure of the keys is minimized.

From the above, can I assume that the maxium bit size support for anyconnect vpn would be 2048 bits since it is using SSL. Not too sure what if signature operations refers to ike vpn which support 4096 bits?

Appreciate any help.

Thanks.

  • VPN
1 REPLY

Cisco ASA AnyConnect VPN Using Certificate Bit Size Support

The maximum key you can generate looks to be 2048 - so 2048 bit support for using anyconnect VPN.

--Jason

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