OpenSSH vs OpenSSL

This page clarifies the differences between OpenSSH and OpenSSL, two related but distinct security-focused software projects.

Core Distinction

OpenSSH: A suite of tools for secure remote login and file transfer over a network using the SSH protocol. It focuses on securing network connections and authenticating users/servers.
OpenSSL: A general-purpose cryptography library and toolkit. It implements the SSL/TLS protocols and provides fundamental cryptographic functions (encryption, decryption, hashing, digital signatures, certificate management) used by many different applications, including potentially OpenSSH.

Comparison Table

Feature/Aspect	OpenSSH	OpenSSL
Primary Purpose	Secure remote connections (shell access, tunneling, file transfer).	Provide cryptographic library functions; Implement SSL/TLS protocols; Manage certificates & keys.
Main Protocol(s)	SSH (Secure Shell) v1 & v2 (primarily v2)	SSL (v2, v3 - deprecated), TLS (v1.0, v1.1, v1.2, v1.3)
Primary Tools/Executables	`ssh` (client), `sshd` (server), `scp`, `sftp`, `ssh-keygen`, `ssh-agent`, `ssh-add`	`openssl` (command-line tool), `libssl` (library), `libcrypto` (library)
Key Use Cases	- Remote command execution- Secure file transfer (SCP/SFTP)- Port forwarding (tunneling)- Secure remote administration	- Creating/Managing X.509 Certificates (CSRs, self-signed, CAs)- Generating private/public keys- Encrypting/Decrypting files- Calculating hashes/HMACs- Testing SSL/TLS connections- Providing crypto functions for other apps (web servers, VPNs, etc.)
Focus	Network connection security, authentication, access control.	Data encryption, digital signatures, certificate validation, cryptographic algorithm implementation.
Nature	A suite of applications and a daemon implementing the SSH protocol.	A library and a command-line utility providing cryptographic primitives and tools.
User Interaction	Direct interaction via client (`ssh user@host`), server configuration (`sshd_config`).	Often used by other applications (e.g., web servers), but also direct via `openssl` command for specific crypto tasks.
Relationship	Uses cryptographic functions (like encryption, key exchange, hashing) which may be provided by OpenSSL (or LibreSSL or built-in crypto) depending on the build/platform.	Provides the underlying cryptographic functions and potentially the TLS library that other applications (including possibly OpenSSH components) can use.
Analogy	The secure armored truck and the secure communication channel between specific points.	The factory that makes the high-security locks, keys, encryption algorithms, and security protocols used by the armored truck (and many other things like banks, websites, etc.).

Key Takeaways

You use OpenSSH (specifically the ssh client) to connect securely to a remote server running the sshd daemon.
You use OpenSSL (specifically the openssl command-line tool or its libraries via another program) to generate keys, create certificate signing requests (CSRs), inspect certificates, encrypt data, or test a web server's TLS configuration.
A web server like Apache or Nginx uses OpenSSL (via libssl and libcrypto) to handle HTTPS (HTTP over TLS) connections. It does not typically use OpenSSH for this.
OpenSSH requires cryptography, and it often relies on OpenSSL (or a similar crypto library like LibreSSL) to provide those cryptographic functions.
They solve different problems: OpenSSH secures connections and access, while OpenSSL provides the tools and building blocks for encryption and identity verification (certificates).

You generally don't choose between them for the same task; they serve different fundamental purposes, although they both contribute to overall system and network security.