Knowledge Base

A demonstration of IntraCluster SSL Encryption

This document provides a step-by-step demonstration of the process to deploy a Self-Signed SSL Certificate, to member instances of a Causal Cluster, aimed at achieving intra-cluster encryption. The steps can be outlined as:

  • Generate and install cryptographic objects

  • Create an SSL policy

  • Configure Causal Clustering with the SSL policy

  • Validate the secure operation of the cluster

Lets go through the demonstration of creation, deployment and verification of the SSL certificate.


A certificate can be signed by a trusted Certificate Authority (CA) or, as in this case, be a self-signed one. Lets first see how we can create a self-signed certificate with OpenSSL. We’ll first need to install OpenSSL in order to create a self-signed certificate. While Linux distributions usually have OpenSSL pre-installed, this is not the case for Windows, where this can be achieved using a Windows binary. Some sample binaries are available at the below links:

On OSX, one can install OpenSSL using macports, as described here:

For purposes of this demonstration, homebrew was used as below:

$ brew install openssl

Once installed, the version and installation directory, amongst other installation features, can be checked by running brew info openssl, or openssl version -a:

$ openssl version -a
OpenSSL 1.0.2o  27 Mar 2018
built on: reproducible build, date unspecified
platform: darwin64-x86_64-cc
options:  bn(64,64) rc4(ptr,int) des(idx,cisc,16,int) idea(int) blowfish(idx)
compiler: /usr/bin/clang -I. -I.. -I../include  -fPIC
OPENSSLDIR: "/opt/local/etc/openssl"


We can then add the installation directory to PATH as echo 'export PATH="/usr/local/opt/openssl/bin:$PATH"' >> ~/.bash_profile

Lets finally get to creating our certificate and key:

In terminal, change the current directory to the openssl installation directory (in this case, /opt/local/bin) and run the command below:

$ sudo openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days XXX

or, for a relatively smaller key length:

$ sudo openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days XXX

Below describes each parameter used in the openssl command above:

  • req: PKCS#10 certificate request and certificate generating utility.

  • x509: outputs a self signed certificate instead of a certificate request.

  • newkey: creates a new certificate request and a new private key. Note the rsa:nbits, where nbits is the number of bits, generates an RSA key nbits in size.

  • keyout: gives the filename to write the newly created private key to.

  • out: specifies the output filename to write to or standard output by default.

  • days: when the -x509 option is being used this specifies the number of days to certify the certificate for (default is 30 days).

Below is the output of the executed openssl generation command:

$ sudo openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365
Generating a 4096 bit RSA private key
writing new private key to 'key.pem'
Enter PEM pass phrase:
Verifying - Enter PEM pass phrase:
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
Country Name (2 letter code) [AU]:UK
State or Province Name (full name) [Some-State]:London
Locality Name (eg, city) []:London
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Neo4j
Organizational Unit Name (eg, section) []:CS
Common Name (e.g. server FQDN or YOUR name) []:CS
Email Address []

Above creates the cert.pem and key.pem files in the current directory.

Below commands then generate the public.crt and private.key files, using the .pem files created above:

$ sudo openssl x509 -outform der -in cert.pem -out public.crt
$ openssl rsa -in key.pem -out private.key


Place the above created private.key in $NEO4J_HOME/certificates/cluster and public.crt in $NEO4J_HOME/certificates/cluster/trusted, then add the following to neo4j.conf of each instance in the cluster:



We’re now ready to initialise all cluster instances. Once these are initialised and available, we can then verify our SSL encryption by using the nmap tool (deployed alongside openssl), to check the available SSL ciphers as below:

$ nmap --script ssl-enum-ciphers -p 7470 localhost
Starting Nmap 7.70 ( ) at 2019-05-30 12:39 BST
Nmap scan report for localhost (
Host is up (0.00022s latency).
Other addresses for localhost (not scanned): ::1

7470/tcp open  unknown
| ssl-enum-ciphers:
|   TLSv1.2:
|     ciphers:
|       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (secp256r1) - A
|       TLS_RSA_WITH_AES_256_CBC_SHA256 (rsa 2048) - A
|       TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 (dh 2048) - A
|       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 (secp256r1) - A
|       TLS_RSA_WITH_AES_128_CBC_SHA256 (rsa 2048) - A
|       TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 (dh 2048) - A
|       TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (secp256r1) - A
|       TLS_RSA_WITH_AES_256_GCM_SHA384 (rsa 2048) - A
|       TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (dh 2048) - A
|       TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (secp256r1) - A
|       TLS_RSA_WITH_AES_128_GCM_SHA256 (rsa 2048) - A
|       TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (dh 2048) - A
|     compressors:
|       NULL
|     cipher preference: server
|_  least strength: A

Nmap done: 1 IP address (1 host up) scanned in 0.54 seconds

Where port 7470 in this case is the dbms.connector.https.advertised_address:port. An additional confirmation would be to find debug messages similar to the following, in the Neo4j debug.log:

2019-05-30 11:34:47.666+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameDecoder] Decoding WebSocket Frame opCode=2
2019-05-30 11:34:47.666+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameDecoder] Decoding WebSocket Frame length=101
2019-05-30 11:34:47.666+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameDecoder] Decoding WebSocket Frame opCode=2
2019-05-30 11:34:47.666+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameDecoder] Decoding WebSocket Frame length=943
2019-05-30 11:34:47.695+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameEncoder] Encoding WebSocket Frame opCode=2 length=8298
2019-05-30 11:34:47.695+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameEncoder] Encoding WebSocket Frame opCode=2 length=114435
2019-05-30 11:34:47.695+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameEncoder] Encoding WebSocket Frame opCode=2 length=2730
2019-05-30 11:34:47.696+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameEncoder] Encoding WebSocket Frame opCode=2 length=31010
2019-05-30 11:34:47.696+0000 DEBUG [io.netty.handler.codec.http.websocketx.WebSocket08FrameEncoder] Encoding WebSocket Frame opCode=2 length=113