Implementing ECC+PFS on LineRate (Part 1/3): Choosing ECC Curves and Preparing SSL Certificates

(Editors note: the LineRate product has been discontinued for several years. 09/2023)
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Overview

In case you missed it, Why ECC and PFS Matter: SSL offloading with LineRate details some of the reasons why ECC-based SSL has advantages over RSA cryptography for both performance and security.

This article will generate all the necessary ECC certificates with the secp384r1 curve so that they may be used to configure an LineRate System for SSL Offload.

Getting Started with LineRate

In order to appreciate the advantages of SSL/TLS Offload available via LineRate as discussed in this article, let's take a closer look at how to configure SSL/TLS Offloading on a LineRate system. This example will implement Elliptical Curve Cryptography and Perfect Forward Secrecy. SSL Offloading will be added to an existing LineRate System that has one public-facing Virtual IP (10.10.11.11) that proxies web requests to a Real Server on an internal network (10.10.10.1). The following diagram demonstrates this configuration:

Figure 1: A high-level implementation of SSL Offload

Overall, these steps will be completed in order to enable SSL Offloading on the LineRate System:

Generate a private key specifying the secp384r1 elliptic curve
Obtain a certificate from a CA
Configure an SSL profile and attach it to the Virtual IP

Note that this implementation will enable only ECDHE cipher suites. ECDH cipher suites are available, but these do not implement the PFS feature. Further, in production deployments, considerations to implement additional types of SSL cryptography might be needed in order to allow backward compatibility for older clients.

Generating a private key for Elliptical Curve Cryptography

When considering the ECC curve to use for your environment, you may choose one from the currently available curves list in the LineRate documentation. It is important to be cognizant of the curve support for the browsers or applications your application targets using. Generally, the NIST P-256, P-384, and P-521 curves have the widest support. This example will use the secp384r1 (NIST P-384) curve, which provides an RSA equivalent key of 7680-bits. Supported curves with OpenSSL can be found by running the openssl ecparam -list_curves command, which may be important depending on which curve is chosen for your SSL/TLS deployment.

Using OpenSSL, a private key is generated for use with ssloffload.lineratesystems.com. The ECC SECP curve over a 384-bit prime field (secp384r1) is specified:

openssl ecparam -genkey -name secp384r1 -out ssloffload.lineratesystems.com.key.pem

This command results in the following private key:

Generating a Certificate Request (CSR) to provide the Certificate Authority (CA)

After the primary key is obtained, a certificate request (CSR) can be created. Using OpenSSL again, the following command is issued filling out all relevant information in the successive prompts:

openssl req -new -key ssloffload.lineratesystems.com.key.pem -out ssloffload.lineratesystems.com.csr.pem

This results in the following CSR:

Obtaining a Certificate from a Certificate Authority (CA)

Rather than using a self-signed certificate, a test certificate is obtained from Entrust. Upon completing the certificate request and receiving it from Entrust, a simple conversion needs to be done to PEM format. This can be done with the following OpenSSL command:

openssl x509 -inform der -in ssloffload.lineratesystems.com.cer -out ssloffload.lineratesystems.com.cer.pem

This results in the following certificate:

Note that the certificate generation process is very familiar with Elliptical Curve Cryptography versus traditional cryptographic algorithms like RSA. Only a few differences are found in the generation of the primary key where an ECC curve is specified.

Continue the Configuration

Now that the certificates needed to configure Elliptical Curve Cryptography have been created, it is now time to configure SSL Offloading on LineRate. Part 2: Configuring SSL Offload on LineRate continues the demonstration of SSL Offloading by importing the certificate information generated in this article and getting the system up and running.

In case you missed it, Why ECC and PFS Matter: SSL offloading with LineRate details some of the reasons why ECC-based SSL has advantages over RSA cryptography for both performance and security.

(Editors note: the LineRate product has been discontinued for several years. 09/2023)

Stay Tuned!

Next week a demonstration on how to verify a correct implementation of SSL with ECC+PFS on LineRate will make a debut on DevCentral. The article will detail how to check for ECC SSL on the wire via WireShark and in the browser. In the meantime, take some time to download LineRate and test out its SSL Offloading capabilities.

~~In case you missed any content, or would like to reference it again, here are the articles related to implementing SSL Offload with ECC and PFS on LineRate:~~

Why ECC and PFS Matter: SSL offloading with LineRate
Implementing ECC+PFS on LineRate (Part 1/3): Choosing ECC Curves and Preparing SSL Certificates
Implementing ECC+PFS on LineRate (Part 2/3): Configuring SSL Offload on LineRate
Implementing ECC+PFS on LineRate (Part 3/3): Confirming the Operation of SSL Offloading

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Updated Sep 26, 2023

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