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
sshclient) to connect securely to a remote server running thesshddaemon. - You use OpenSSL (specifically the
opensslcommand-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
libsslandlibcrypto) 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.