TLS and SSH are both widely used protocols for creating secure connections between two systems over an untrusted network. Although they share some fundamental goals, they are designed for different use cases. In this updated guide, we will explore when you should use which, along with a look at the latest developments in both protocols.
About TLS
TLS (Transport Layer Security) is what is most commonly used to secure connections to the web. It is the successor to SSL (Secure Sockets Layer), from which wolfSSL gets part of its name. Today, almost all websites use TLS, and most web browsers expect a website to use TLS when connecting. Beyond the web, TLS secures email, VoIP, VPNs, and countless other applications.
In general, TLS is designed so that a client can authenticate that the intended server is where the data transfer is happening and encrypt the data in transit. TLS 1.3, the current version of the protocol, has seen widespread adoption and offers improved security and reduced handshake latency compared to its predecessors.
About SSH
SSH (Secure SHell) is well known to anyone who has used a Linux or Unix-based system. It is typically used to remotely log into a server and execute commands, as well as transfer files via SCP and SFTP. SSH is ideal for remote shell or desktop access to machines over an unsecured network.
In addition to wolfSSL, we have wolfSSH, which provides lightweight SSH client and server support for embedded platforms. Recent versions have added DH Group 16 and HMAC-SHA2-512 support, keyboard-interactive authentication (RFC 4256), Ed25519 public key support, and TPM-based RSA authentication for enhanced security in embedded and IoT applications.
Key Differences
Authentication
SSH allows for many different authentication methods, from basic passwords to keys and certificates. The recent addition of keyboard-interactive authentication in wolfSSH provides even more flexibility for interactive authentication workflows. TLS typically relies on a trusted CA (Certificate Authority) for authentication. Both TLS and SSH support OCSP for certificate revocation status.
Feature Set
SSH not only handles basic authentication and encryption but provides the next layer of features, such as shell access, file transfer, and port forwarding. TLS is typically a secure wrapper around existing plain protocols.
Another feature SSH provides is the concept of channels. This allows multiplexing of multiple services over one SSH connection. For example, a single connection can have a shell, file transfer, and multiple ports forwarded simultaneously.
Performance
TLS 1.3 has a very low number of round trips required to handshake between the client and server. The handshake for SSH is more involved, which can make new connections more expensive on high-latency networks.
Once the connection is established, the performance of each should be relatively similar, depending on the encryption algorithms used.
Ease Of Use
TLS is designed to be relatively easy to use, with a low barrier to entry for the client user. SSH can be more difficult to configure and typically has more steps for the end user due to the mutual authentication requirements.
The Post-Quantum Factor
One of the most significant developments affecting both TLS and SSH is the move toward post-quantum cryptography. With the threat of “harvest now, decrypt later” attacks, where adversaries collect encrypted traffic today to decrypt it once quantum computers become powerful enough, preparing for the post-quantum era is essential.
Both wolfSSL and wolfSSH now support post-quantum hybrid key exchange. For TLS 1.3, wolfSSL supports ML-KEM (the standardized version of Kyber, specified in NIST FIPS 203) in both standalone and hybrid modes, combining it with traditional elliptic curves like P-256, P-384, and X25519 for defense-in-depth. wolfSSL is actively working toward FIPS validation for ML-KEM and ML-DSA to meet CNSA 2.0 requirements.
For SSH, wolfSSH supports hybrid post-quantum key exchange using ML-KEM, including mlkem768nistp256-sha256, mlkem768x25519-sha256, and mlkem1024nistp384-sha384. This enables interoperability with OpenSSH 9.9+, AWS Transfer Family, and other implementations following the IETF draft for PQ/T hybrid key exchange in SSH, ensuring your SSH connections are protected against both current and future quantum threats while maintaining FIPS compliance.
Expanding the wolfSSL Ecosystem
Beyond TLS and SSH, wolfSSL has expanded its security ecosystem with several complementary products:
- wolfIP is a lightweight TCP/IP stack with no dynamic memory allocations, designed for resource-constrained embedded systems. It provides a BSD-like socket API and supports protocols from Ethernet and ARP up through TCP, UDP, DHCP, and DNS, with HTTP/HTTPS server support powered by wolfSSL TLS. When you need secure networking on bare-metal or minimal RTOS environments, wolfIP combined with wolfSSL gives you a complete stack.
- wolfGuard is a FIPS-compliant refactor of WireGuard VPN that replaces the original cryptographic primitives with FIPS 140-3 approved algorithms. Where WireGuard uses Curve25519 and ChaCha20-Poly1305, wolfGuard uses SECP256R1 and AES-256-GCM. This makes wolfGuard ideal for government and regulated industries that require both modern VPN performance and FIPS compliance.
Summary
Both TLS and SSH are essential for securing traffic over untrusted networks. TLS is very useful for wrapping existing protocols with a layer of security, whereas SSH is ideal for remote command access to a system and network tunnels.
When choosing between them, consider your use case: if you need to secure web traffic, APIs, or application protocols, TLS 1.3 is typically the right choice. If you need interactive remote access, file transfer capabilities, or port forwarding, SSH provides those features built-in.
Regardless of which protocol you choose, the transition to post-quantum cryptography is now, and both wolfSSL and wolfSSH are ready to help you make that transition while maintaining compatibility and compliance.
If you wish to learn more or have questions about any of the above, please contact us at facts@wolfSSL.com or +1 425 245 8247.
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