Encryption is a cornerstone of virtual private network (VPN) security. This article analyzes the most commonly used encryption algorithms, such as AES-128, AES-256, and ChaCha20, comparing their security level, performance, and applicability. It also addresses which one might be most suitable depending on the device and environment.

1. Introduction

VPNs encrypt network traffic to ensure user privacy and prevent unauthorized access. The type and level of encryption used can affect both the security and speed of the connection. The appropriate choice depends on factors such as hardware, VPN protocol, and the objective (anonymity, speed, or resistance to attacks).

2. Main encryption algorithms

2.1 AES (Advanced Encryption Standard)

AES is a symmetric encryption standard adopted by the US government in 2001. It has key sizes of 128, 192, and 256 bits, but the most common in VPNs are AES-128 and AES-256.

  1. AES-128: Uses a 128-bit key and 10 rounds of encryption. Considered secure and efficient.
  2. AES-256: Uses a 256-bit key and 14 rounds of encryption. Offers greater theoretical security at the cost of higher CPU usage.

2.2 ChaCha20

ChaCha20 is a stream cipher developed by Daniel J. Bernstein. It is optimized for devices without AES hardware acceleration (such as smartphones) and is frequently used with the WireGuard protocol.

\"ChaCha20 is approximately 3 times faster than pure software AES on mobile devices.\" — Bernstein et al., 2008

3. Technical Comparison

Algorithm Key Length Speed Security Recommended for
AES-128128 bitsHigh (with hardware acceleration)Very highDesktop, modern routers
AES-256256 bitsModerateExtremely highGovernments, sensitive data
ChaCha20256 bitsHigh (in software)Very highMobiles, ARM devices

4. Performance Considerations

Using AES-256, while more secure, can reduce performance on older devices or those without hardware acceleration. AES-128 is widely considered secure enough for most users.

ChaCha20 has gained popularity for its excellent performance on mobile devices, being integrated by default in browsers like Chrome and in protocols like TLS 1.3 and WireGuard.

5. Theoretical Attacks and Resistance

  1. There are no known practical attacks against AES-128 or AES-256.
  2. ChaCha20 has withstood exhaustive cryptographic testing and is considered secure for production.
  3. AES-256 has greater resistance to brute-force attacks due to its key length, but in practice both (128 and 256) are far from vulnerable.

6. Recommendations according to the case

  1. Mobile users: ChaCha20 (for performance).
  2. Desktop users: AES-128 (balance between security and speed).
  3. Government or critical environments: AES-256.
  4. Legacy routers: AES-128 or consider switching to ChaCha20 if WireGuard is supported.

7. Conclusion

The choice of encryption level in a VPN should balance security and performance. AES-256 offers maximum protection, but AES-128 and ChaCha20 are more than sufficient for most modern users and devices.

8. References

  1. Bernstein, D. J. (2008). ChaCha, a variant of Salsa20. [Online]. Available at: https://cr.yp.to/chacha/chacha-20080128.pdf
  2. NIST. (2001). Announcing the Advanced Encryption Standard (AES). FIPS PUB 197.
  3. WireGuard. (2020). Technical Overview. https://www.wireguard.com/protocol/
  4. OpenVPN. (2024). Encryption Overview. https://openvpn.net/security-overview/
  5. Google Security Blog. (2016). ChaCha20 and Poly1305 for TLS. https://security.googleblog.com/2016/05/chacha20-and-poly1305-for-tls.html