Why We Replaced RSA with Ed25519 (EdDSA RFC 8037)

As web architectures migrated from centralized application servers to edge runtimes (Cloudflare Workers, Vercel Edge Runtime) and serverless containers, the cryptographic overhead of token verification became a major bottleneck.

The Problem with RSA

Standard RSA-2048 and RSA-4096 keys have noticeable latency during public key mathematical operations:

Large key payloads (often 1KB+ in JWKS JSON).

High CPU compute cycles during signature verification.

Increased cold-start penalties on memory-constrained edge workers.

The Solution: Ed25519

Ed25519 (EdDSA) uses twisted Edwards curves over a 256-bit prime field:

**Compact size**: Public keys are exactly 32 bytes (256 bits).

**Fast verification**: Signatures verify in microseconds using the native Web Crypto API without external OpenSSL bindings.

**Side-channel resistance**: All operations are constant-time by design.

By publishing active Ed25519 keys at `/.well-known/jwks.json`, AuthSetu applications verify user authentication locally without making any round-trips to the AuthSetu database.

Why We Replaced RSA with Ed25519 (EdDSA RFC 8037)

The Problem with RSA

Standard RSA-2048 and RSA-4096 keys have noticeable latency during public key mathematical operations:

Large key payloads (often 1KB+ in JWKS JSON).

High CPU compute cycles during signature verification.

Increased cold-start penalties on memory-constrained edge workers.

The Solution: Ed25519

Ed25519 (EdDSA) uses twisted Edwards curves over a 256-bit prime field:

**Compact size**: Public keys are exactly 32 bytes (256 bits).

**Fast verification**: Signatures verify in microseconds using the native Web Crypto API without external OpenSSL bindings.

**Side-channel resistance**: All operations are constant-time by design.

By publishing active Ed25519 keys at `/.well-known/jwks.json`, AuthSetu applications verify user authentication locally without making any round-trips to the AuthSetu database.

Why We Replaced RSA with Ed25519 (EdDSA RFC 8037) for AuthSetu Session Tokens

Why We Replaced RSA with Ed25519 (EdDSA RFC 8037)

The Problem with RSA

The Solution: Ed25519

Engineering Team

Subscribe to AuthSetu Dispatch

Related Articles

Architecting DigiLocker Document Verification Under the Indian DPDP Act

Why We Replaced RSA with Ed25519 (EdDSA RFC 8037) for AuthSetu Session Tokens

Why We Replaced RSA with Ed25519 (EdDSA RFC 8037)

The Problem with RSA

The Solution: Ed25519

Engineering Team

Subscribe to AuthSetu Dispatch

Related Articles

Architecting DigiLocker Document Verification Under the Indian DPDP Act