Ed25519 signature

Overview & Cryptographic Context

Ed25519 (specified in IETF RFC 8032 and NIST FIPS 186-5) is the Edwards-curve Digital Signature Algorithm (EdDSA) over the twisted Edwards curve -x² + y² = 1 - (121665/121666)x²y² (mod 2²⁵⁵-19) paired with SHA-512. Unlike traditional ECDSA, which requires a fresh cryptographic random nonce k for every signature (and suffers catastrophic private-key recovery if a nonce is ever reused), Ed25519 derives the per-message nonce r = SHA-512(prefix ‖ M) mod ℓ deterministically from the secret key's upper SHA-512 half and the message itself.

This workflow reproduces RFC 8032 §7.1 (TEST 2), signing a 1-byte message (0x72) under a 32-byte secret key seed to produce the exact 64-byte signature R ‖ S.

Pipeline Architecture & Wiring Flow

1. Seed & Message Ingress (Workflow Input): Supplies the 32-byte Ed25519 secret seed PrivateKey and the 1-byte Message (0x72).
2. Deterministic Signing (Ed25519 Sign): Expands the 32-byte seed with SHA-512 into the clamped secret scalar s and nonce prefix, derives public key A = [s]B, computes R = [r]B, and solves S = (r + SHA-512(R ‖ A ‖ M) · s) mod ℓ.
3. Signature Output (Workflow Output): Emits the 64-byte signature (R || S).

Nodes & Configuration

Node reference →

Inputs, Outputs & Test Vector Verification

Verification Source: RFC 8032 §7.1 (TEST 2, message 0x72)

Inputs

Expected Outputs