# Encryption

hstream supported encryption between servers and clients using TLS, in this chapter, we will not introduce more details about TLS, instead, we will only show steps and configurations to enable it.

# Steps

If you don't have any existed CA(Certificate Authority), you can create one locally, and TLS requires that each server have a key and the corresponding signed certificate, openssl is a good tool to generate them, after that, you need to configure the files paths in the servers and clients sides to enable it.

# Create a local CA

Create or choose a directory for storing keys and certificates:

mkdir tls
cd tls

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Create a database file and serial number file:

touch index.txt
echo 1000 > serial

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Get the template openssl.cnf file(the template file is intended for testing and development, do not use it in the production environment directly):

wget https://raw.githubusercontent.com/hstreamdb/hstream/main/conf/openssl.cnf

Generate the CA key file:

openssl genrsa -aes256 -out ca.key.pem 4096

Generate the CA certificate file:

openssl req -config openssl.cnf -key ca.key.pem \
    -new -x509 -days 7300 -sha256 -extensions v3_ca \
    -out ca.cert.pem

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# Create key pair and sign certificate for a server

Here we only generate a key and certificate for one server, you should create them for all hstream servers that have a different hostname, or create a certificate including all hostnames(IP or DNS) in SANs.

Generate the server key file:

openssl genrsa -out server01.key.pem 2048

Generate the server certificate request, when you input Common Name, you should write the correct hostname(e.g., localhost):

openssl req -config openssl.cnf \
    -key server01.key.pem -new -sha256 -out server01.csr.pem

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generate the server certificate with the generated CA:

openssl ca -config openssl.cnf -extensions server_cert \
    -days 1000 -notext -md sha256 \
    -in server01.csr.pem -out signed.server01.cert.pem

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# Configure the server and clients

The options for servers:

# TLS options
#
# enable tls, which requires tls-key-path and tls-cert-path options
enable-tls: true

#
# key file path for tls, can be generated by openssl
tls-key-path: /path/to/the/server01.key.pem

# the signed certificate by CA for the key(tls-key-path)
tls-cert-path: /path/to/the/signed.server01.cert.pem

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Java client:

HStreamClient.builder()
  .serviceUrl(serviceUrl)
  // optional, enable tls
  .enableTls()
  .tlsCaPath("/path/to/ca.cert.pem")

  .build()

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