X25519 vs RSA for Email Encryption: Practical Benchmarks in 2026

Bob Bricoleur — Sat, 04 Apr 2026 16:21:01 +0000

Why I switched from RSA to X25519 for email encryption

While building an encrypted email service, I had to choose between RSA and X25519 (Curve25519) for key exchange. Here are real benchmarks from our Node.js implementation:

Key Generation

Algorithm	Time	Key Size
X25519	~0.1ms	32 bytes
RSA-2048	~50ms	256 bytes
RSA-4096	~500ms	512 bytes

X25519 is 500-5000x faster for key generation.

Our ECIES Pattern

We use X25519 + HKDF + AES-256-GCM (ECIES pattern):

1. Generate ephemeral X25519 keypair
2. ECDH(ephemeral_priv, recipient_pub) → shared_secret
3. HKDF(shared_secret, info) → aes_key (32 bytes)
4. AES-256-GCM(aes_key, plaintext) → ciphertext + auth_tag

The envelope is a compact JSON:

{
  "v": 1,
  "alg": "X25519-HKDF-AES256GCM",
  "epk": "<base64 ephemeral public key>",
  "iv": "<12 bytes>",
  "tag": "<16 bytes>",
  "ct": "<ciphertext>"
}

Why not PGP?

PGP is the standard for email encryption but:

Key management is painful for regular users
No forward secrecy (same key for all messages)
Large keys and slow operations

X25519 ECIES gives us ephemeral keys per message (forward secrecy) with minimal overhead.

Browser Implementation

Web Crypto API supports X25519 natively in modern browsers, so we can encrypt/decrypt client-side without any library:

const keyPair = await crypto.subtle.generateKey(
  { name: "X25519" },
  true,
  ["deriveKey"]
);

Trade-offs

Pro: Fast, small keys, forward secrecy, browser-native
Con: Less widely adopted than RSA, no direct signing (use Ed25519 separately)

Would love to hear from others implementing email encryption. What patterns are you using?

Built with Node.js crypto module (server) + Web Crypto API (client)

What's your email setup for privacy in 2026?

Bob Bricoleur — Sat, 04 Apr 2026 15:23:56 +0000

Curious what people using these days for email privacy. The
landscape seems to have changed a lot:

ProtonMail went mainstream but some complain about lock-in
Tutanota rebranded to Tuta, mixed reviews
Self-hosted is more accessible but deliverability is still hard
New players popping up with different approaches (E2E,sovereign hosting, etc.)

What's your current setup? Especially interested in:

Provider or self-hosted?
E2E encryption — do you actually use it?
Custom domain or provider domain?
How do you handle the fact that the other side usually uses Gmail anyway?

Forem: Bob Bricoleur