Installation Guide

This guide will walk you through installing Net::SSH and its dependencies.

System Requirements

Ruby: Net::SSH requires Ruby version 2.6 or newer. You can check your Ruby version with ruby -v.
OpenSSL: You need Ruby's OpenSSL bindings with a version of OpenSSL greater than 1.0.1. Most modern Ruby installations include this. You can verify it by running:
```
ruby -ropenssl -e 'puts OpenSSL::OPENSSL_VERSION'
```

Standard Installation

The simplest way to install Net::SSH is using RubyGems:

gem install net-ssh

You may need to use sudo depending on your system's configuration.

Using Bundler

For managing dependencies in a project, it's recommended to use Bundler. Add Net::SSH to your Gemfile:

source 'https://rubygems.org'

gem 'net-ssh'

Then, run bundle install.

Verifying the Gem Signature

For enhanced security, all Net::SSH gem releases are cryptographically signed. To verify the gem's integrity upon installation, follow these steps:

Add the public key as a trusted certificate. You only need to do this once.

# Download the public certificate
curl -O https://raw.githubusercontent.com/net-ssh/net-ssh/master/net-ssh-public_cert.pem

# Add it to RubyGems' trusted certificates
gem cert --add net-ssh-public_cert.pem

Install the gem with high security.
```
gem install net-ssh -P HighSecurity
```

If the signature is valid, the gem will install. If not, RubyGems will raise an error, protecting you from potentially tampered code.

Optional Dependencies for Extra Features

Net::SSH uses optional gems to enable certain modern cryptographic algorithms. If you need support for these features, you must add the corresponding gems to your project's Gemfile.

ED25519 and Curve25519 Support:

For ssh-ed25519 keys and the curve25519-sha256 key exchange algorithm, add the following gems:
```
gem 'ed25519', '~> 1.2'
gem 'x25519'
gem 'bcrypt_pbkdf', '~> 1.0' # Not required for JRuby
```
ChaCha20-Poly1305 Cipher Support:

To use the chacha20-poly1305@opnessh.com cipher, which offers high performance, add the rbnacl gem:
```
gem 'rbnacl', '~> 7.1'
```
Ruby 3.0+ WebRick dependency:

If you are using Ruby 3.0 or greater, you might need to add webrick if it's not already part of your dependencies, as it was removed from the standard library.
```
gem 'webrick'
```

Example Gemfile with All Features

source 'https://rubygems.org'

gem 'net-ssh'

# For ED25519 and Curve25519 support
gem 'ed25519', '~> 1.2'

# JRuby does not support bcrypt_pbkdf
gem 'bcrypt_pbkdf', '~> 1.0', platforms: [:mri, :mingw]

gem 'x25519', platforms: [:mri, :mingw]

# For ChaCha20-Poly1305 cipher support
gem 'rbnacl', '~> 7.1'

# Required for some development/test tasks in Ruby 3.0+
gem 'webrick', require: false if RUBY_VERSION.to_i >= 3