In OpenVPN 2.4+, both tls-auth and tls-crypt serve as additional security layers for the TLS handshake process, but they implement protection differently:

# tls-auth example (traditional approach)
tls-auth ta.key 1

# tls-crypt example (newer encryption)
tls-crypt tc.key

tls-auth provides HMAC authentication while tls-crypt adds full packet encryption:

• tls-auth: Verifies packet authenticity but doesn't encrypt metadata
• tls-crypt: Encrypts entire control channel including packet headers

Here's how to upgrade your config from tls-auth to tls-crypt:

# Generate tls-crypt key (requires OpenVPN 2.4+)
openvpn --genkey --secret tc.key

# Client configuration example
client
tls-client
dev tun
proto udp
remote vpn.example.com 1194

-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----

tls-crypt tc.key
cipher AES-256-GCM
ncp-ciphers AES-256-GCM
auth SHA512

While tls-crypt provides better security, it adds ~30 bytes overhead per packet. For most modern hardware, this impact is negligible:

# Benchmark command
openssl speed -evp aes-256-gcm

For existing deployments, consider this phased approach:

1. Generate new tls-crypt keys
2. Deploy to test clients
3. Monitor performance for 48h
4. Roll out to production

tls-crypt specifically protects against:

• Denial of Service (DoS) attacks
• Metadata analysis
• Pre-encryption traffic inspection

In OpenVPN 2.4+, both tls-auth and tls-crypt serve as additional security layers for TLS handshakes, but they operate at different protection levels:

// Traditional TLS-Auth implementation
tls-auth ta.key 0 # Server config
tls-auth ta.key 1 # Client config

TLS-Auth provides HMAC-based authentication of control packets:

• Uses static key (typically 2048-bit)
• Verifies packet authenticity but doesn't encrypt
• Prevents DoS attacks and unauthorized connections

# Example tls-auth handshake flow
1. Client → Server: [UNENCRYPTED] Control Frame + HMAC
2. Server verifies HMAC using shared ta.key
3. Only then proceeds with TLS handshake

Introduced in OpenVPN 2.4, TLS-Crypt adds encryption:

// Modern TLS-Crypt implementation
tls-crypt tc.key # Same on client and server

Key advantages over TLS-Auth:

• Full encryption of control channel (not just authentication)
• Prevents passive observation of handshake metadata
• Uses same key file format but enables AES-256-CBC encryption

Upgrading your existing config to TLS-Crypt:

# Generate new key (replace ta.key)
openvpn --genkey --secret tc.key

# Update client config
tls-crypt tc.key
cipher AES-256-CBC
auth SHA512

For maximum protection with OpenVPN 2.4+:

1. Always prefer tls-crypt over tls-auth when possible
2. Rotate keys periodically (same frequency as TLS certs)
3. Combine with strong cipher suites (AES-256-GCM preferred)
4. Consider tls-crypt-v2 for per-client keys in newer versions

The key security benefit comes from TLS-Crypt's ability to encrypt the entire control channel before any TLS negotiation occurs, eliminating the window where metadata could be observed during initial handshake phases.