OpenSSL

OpenSSL provides the cryptographic libraries libcrypto (crypto(7ssl)) and libssl (ssl(7ssl)), as well as the utility openssl(1ssl).

Installation

Most Linux and BSD distributions offer an openssl package.

Certificates

It is highly recommended to not use openssl(1ssl)-generated certificates for web encryption. Clients have no reason to trust a self-signed certificate unless you

1. operate your own certificate authority (strongly not recommended)

2. configure all client machines

Usage

To generate a certificate and private key simultaneously, try:

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /path/to/domain-name.com/key.pem -out /path/to/domain-name.com/cert.pem

Diffie-Hellman Parameters

ssl(7ssl) defaults to 1024-bit keys, which lags behind the modern standard of 2048-bits. This is a particular problem for software that defer cryptographic decisions to ssl(7ssl) at runtime, such as nginx(8). One of the most common cryptographic decisions that is affected by this situation is the selection of parameters for Diffie-Hellman key exchanges.

To generate a stronger configuration, try:

openssl dhparam -out /path/to/dhparam.pem 4096

For details on how to use this configuration, see the following articles for NGINX.

See also

openssl(1ssl)

crypto(7ssl)

ssl(7ssl)

LibreSSL

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