VPN Encryption Explained - AES-256 & ChaCha20
How VPN encryption actually works, in plain English. Understand AES-256, ChaCha20, key exchange, and what really matters when choosing a secure VPN.
What Is VPN Encryption?
VPN encryption scrambles your internet traffic into unreadable ciphertext before it leaves your device. Only the VPN server holds the key to unscramble it. To anyone in between - your ISP, a public Wi-Fi operator, or a network snoop - your data looks like meaningless noise. Encryption is the core mechanism that makes a VPN private.
AES-256: The Standard
AES-256 (Advanced Encryption Standard with a 256-bit key) is the encryption every provider in our lineup uses, specifically the AES-256-GCM variant. It's the same standard trusted by governments for classified information. The "256" refers to the key length: there are 2^256 possible keys, a number so large that brute-forcing one is infeasible with any current or foreseeable technology. When marketing says "military-grade encryption," this is it.
The Handshake & Key Exchange
Before any data flows, your device and the VPN server perform a handshake - a negotiation that securely establishes a shared secret key without ever sending that key across the network. This uses public-key cryptography (like Curve25519 in WireGuard or RSA/ECDH in OpenVPN). Good VPNs also use perfect forward secrecy, generating fresh keys regularly so that even if one key were somehow compromised, past and future sessions stay protected.
How Protocols Use Encryption
The protocol is the framework that wraps encryption, authentication, and data transport together:
- WireGuard / NordLynx: uses ChaCha20 for encryption and Curve25519 for key exchange - lean and fast
- OpenVPN: uses AES-256-GCM with a mature, heavily audited codebase
- Lightway (ExpressVPN): supports both AES-256 and ChaCha20, optimized for quick connections
- IKEv2/IPsec: uses AES-256, excellent for stable mobile connections
Encryption by Provider
| Provider | Encryption | Kill Switch | DNS Leak Protection | Privacy Score |
|---|---|---|---|---|
| Mullvad | AES-256-GCM | Yes | Yes | 9.7/10 |
| ProtonVPN | AES-256-GCM | Yes | Yes | 9.6/10 |
| NordVPN | AES-256-GCM | Yes | Yes | 9.5/10 |
| IVPN | AES-256-GCM | Yes | Yes | 9.4/10 |
| ExpressVPN | AES-256-GCM | Yes | Yes | 9.4/10 |
| Surfshark | AES-256-GCM | Yes | Yes | 8.7/10 |
| CyberGhost | AES-256-GCM | Yes | Yes | 8.6/10 |
| Private Internet Access | AES-256-GCM | Yes | Yes | 8.5/10 |
| Windscribe | AES-256-GCM | Yes | Yes | 8.3/10 |
| hide.me | AES-256-GCM | Yes | Yes | 8.2/10 |
| VyprVPN | AES-256-GCM | Yes | Yes | 8.1/10 |
| PrivadoVPN | AES-256-GCM | Yes | Yes | 8/10 |
| Mozilla VPN | AES-256-GCM | Yes | Yes | 8/10 |
| TunnelBear | AES-256-GCM | Yes | Yes | 7.9/10 |
| PureVPN | AES-256-GCM | Yes | Yes | 7.8/10 |
| IPVanish | AES-256-GCM | Yes | Yes | 7.6/10 |
| ZoogVPN | AES-256-GCM | Yes | Yes | 7.5/10 |
| FastestVPN | AES-256-GCM | Yes | Yes | 7.4/10 |
| StrongVPN | AES-256-GCM | Yes | Yes | 7.2/10 |
| Hotspot Shield | AES-256-GCM | Yes | Yes | 6.8/10 |
Every provider we recommend uses AES-256-GCM - the encryption itself is not a differentiator. What separates them is everything around the encryption: audited no-log policies, kill switches, leak protection, and jurisdiction.
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What Actually Matters
Because all reputable VPNs use the same strong encryption, the cipher is rarely where you should focus. Prioritize these instead:
- Independent audits: proof the no-log policy and infrastructure hold up (see our no-log VPN guide)
- Kill switch: cuts your connection if the VPN drops, preventing leaks
- DNS/IP leak protection: ensures no requests escape the encrypted tunnel
- Jurisdiction: where the provider is legally based affects what it can be compelled to do
- Open-source apps: let anyone verify the encryption is implemented correctly
ProtonVPN scores highest on privacy (9.6/10) by combining AES-256 with Swiss jurisdiction and fully open-source, audited apps. NordVPN (9.5/10) pairs the same encryption with the most extensive audit history. Encryption gets you in the door; these factors decide real-world trust.