What if we treated our local networks with the same suspicion as the public internet? The idea of encrypting all intra-LAN communication using certificate-based authentication presents an intriguing paradigm shift. Let's examine a practical implementation using OpenSSL and Python:

# Generate CA certificate (one-time setup)
openssl req -x509 -newkey rsa:4096 -sha256 -days 3650 -nodes \
  -keyout ca.key -out ca.crt -subj "/CN=MyCompanyCA"

# Generate server certificate
openssl req -newkey rsa:2048 -nodes -keyout server.key \
  -out server.csr -subj "/CN=svn.mycompany.local"
openssl x509 -req -in server.csr -CA ca.crt -CAkey ca.key -CAcreateserial \
  -out server.crt -days 365 -sha256

When considering encryption for all LAN traffic, we have several architectural choices:

• IPSec: Kernel-level encryption with policies
• TLS Everywhere: Service-specific implementation
• SSH Tunneling: For point-to-point secure channels

Here's how to enforce TLS for a Python web service:

from flask import Flask
import ssl

app = Flask(__name__)

context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2)
context.load_cert_chain('server.crt', 'server.key')
context.verify_mode = ssl.CERT_REQUIRED
context.load_verify_locations('ca.crt')

@app.route('/')
def hello():
    return "This connection is securely authenticated"

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=443, ssl_context=context)

The encryption overhead varies significantly based on implementation. Benchmarks on a 10Gbps LAN show:

For maintainability, consider using HashiCorp Vault for dynamic certificate issuance:

# Vault PKI configuration
vault secrets enable pki
vault secrets tune -max-lease-ttl=87600h pki
vault write pki/root/generate/internal \
    common_name=mycompany.internal \
    ttl=87600h

# Issue a certificate
vault write pki/issue/internal \
    common_name=dev-laptop42.mycompany.internal \
    ttl=24h

Real-world implementation reveals several pain points:

• Legacy devices without TLS support
• Multicast/broadcast traffic encryption
• Certificate revocation handling

For network devices, consider using MACsec (IEEE 802.1AE) as a fallback:

# Linux MACsec configuration
ip link add macsec0 link eth0 type macsec
ip macsec add macsec0 tx sa 0 pn 1 on key 01 12345678901234567890123456789012
ip macsec add macsec0 rx port 1 address c6:19:52:8f:e3:13
ip macsec add macsec0 rx port 1 address c6:19:52:8f:e3:13 sa 0 pn 1 on \
    key 02 09876543210987654321098765432109
ip link set macsec0 up

Traditional LAN security often relies on perimeter defenses like firewalls and network-based IDS. However, insider threats and lateral movement attacks make this model risky. By implementing mandatory encryption for all traffic - even internal communications - we create a zero-trust environment where:

• Each device authenticates using unique certificates
• All services require mutual authentication
• Network-level attacks become practically useless

First, establish your own Certificate Authority (CA) using OpenSSL:

# Create root CA
openssl genrsa -out rootCA.key 4096
openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 1024 -out rootCA.crt

# Generate server certificate
openssl genrsa -out server.key 2048
openssl req -new -key server.key -out server.csr
openssl x509 -req -in server.csr -CA rootCA.crt -CAkey rootCA.key -CAcreateserial -out server.crt -days 365 -sha256

For web services, configure mandatory HTTPS with client certificate verification in Nginx:

server {
    listen 443 ssl;
    ssl_certificate /path/to/server.crt;
    ssl_certificate_key /path/to/server.key;
    ssl_client_certificate /path/to/rootCA.crt;
    ssl_verify_client on;
    # Rest of configuration
}

Replace password authentication with certificate-based SSH:

# On CA server
ssh-keygen -s rootCA.key -I host_id -h -n hostname /etc/ssh/ssh_host_rsa_key.pub

# In sshd_config
HostCertificate /etc/ssh/ssh_host_rsa_key-cert.pub
TrustedUserCAKeys /etc/ssh/rootCA.pub

While IPSec provides network-layer encryption, it can be complex to manage. Consider these alternatives:

Expect these operational considerations:

• Certificate revocation requires OCSP stapling implementation
• Legacy devices may need compatibility layers
• Debugging encrypted traffic requires careful logging

Use iptables to block all non-encrypted traffic:

# Allow established encrypted connections
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Block plaintext HTTP
iptables -A INPUT -p tcp --dport 80 -j DROP

# Allow only encrypted protocols
iptables -A INPUT -p tcp --dport 443 -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j ACCEPT