Upgrading the self-signed certificate on ASA

amigan_99 used Ask the Experts™
Scanning the outside of one of our Cisco ASA it was noticed the RSA public key
is less than 2048 bits. If I upgrade this, is there any chance it could negatively impacts
IP Sec remote access VPN conenctivity? Or could it affect connectivity of phone proxy?

"Self-signed certificate, RSA public key is less than
2048 bits, Insecure signature algorithm"
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IPSec require SA agreement and exchange for pt to tpt so both end need to make sure that is supported and agreed during the exchange then the IPSec tunnel will be setup. In your upgrade do make sure the SA policy setting is configured
If RSA encryption is configured and signature mode is negotiated (and certificates are used for signature mode), the peer will request both signature and encryption keys. Basically, the router will request as many keys as the configuration will support. If RSA encryption is not configured, it will just request a signature key.

As a whole besides IPsec, you should also know the dependencies using the keys

1) The ASA needs a CA certificate for each trustpoint and one or two certificates for itself, depending upon the configuration of the keys used by the trustpoint. If the trustpoint uses separate RSA keys for signing and encryption, the ASA needs two certificates, one for each purpose. In other key configurations, only one certificate is needed.

2) The ASA supports automatic enrollment with SCEP and with manual enrollment, which lets you paste a base-64-encoded certificate directly into the terminal. For site-to-site VPNs, you must enroll each ASA. For remote access VPNs, you must enroll each ASA and each remote access VPN client.

Performance Note:

Many SSL connections using identity certificates with RSA key pairs that exceed 1024 bits can cause a high CPU usage on the security appliance and rejected clientless logins.

amigan_99Network Engineer


Thanks much!

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