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implementing-digital-signatures-with-ed25519

Ed25519 is a high-performance digital signature algorithm using the Edwards curve Curve25519. It provides 128-bit security with 64-byte signatures and 32-byte keys, offering significant advantages ove

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23
Source
plurigrid/asi
Updated
2026-04-26
Slug
plurigrid--asi--implementing-digital-signatures-with-ed25519
View on GitHubRaw SKILL.md

// install — copy + paste into any project

mkdir -p .claude/skills && curl -fsSL https://raw.githubusercontent.com/plurigrid/asi/HEAD/plugins/asi/skills/implementing-digital-signatures-with-ed25519/SKILL.md -o .claude/skills/implementing-digital-signatures-with-ed25519.md

Drops the SKILL.md into .claude/skills/implementing-digital-signatures-with-ed25519.md. Works with Claude Code, Cursor, and any agent that loads SKILL.md files from .claude/skills/.

Implementing Digital Signatures with Ed25519

Overview

Ed25519 is a high-performance digital signature algorithm using the Edwards curve Curve25519. It provides 128-bit security with 64-byte signatures and 32-byte keys, offering significant advantages over RSA and ECDSA including deterministic signatures (no random nonce needed), resistance to side-channel attacks, and fast verification. This skill covers implementing Ed25519 for document signing, code signing, and API authentication.

When to Use

  • When deploying or configuring implementing digital signatures with ed25519 capabilities in your environment
  • When establishing security controls aligned to compliance requirements
  • When building or improving security architecture for this domain
  • When conducting security assessments that require this implementation

Prerequisites

  • Familiarity with cryptography concepts and tools
  • Access to a test or lab environment for safe execution
  • Python 3.8+ with required dependencies installed
  • Appropriate authorization for any testing activities

Objectives

  • Generate Ed25519 key pairs for signing
  • Sign messages and files with Ed25519
  • Verify signatures against public keys
  • Implement multi-signature verification
  • Build a simple code signing system
  • Compare Ed25519 performance with RSA and ECDSA

Key Concepts

Ed25519 vs RSA vs ECDSA

Property Ed25519 RSA-3072 ECDSA P-256
Security 128-bit 128-bit 128-bit
Public key size 32 bytes 384 bytes 64 bytes
Signature size 64 bytes 384 bytes 64 bytes
Key generation ~50 us ~100 ms ~1 ms
Sign ~70 us ~5 ms ~200 us
Verify ~200 us ~200 us ~500 us
Deterministic Yes No (PSS) No (unless RFC 6979)

Key Properties

  • Deterministic: Same message + key always produces same signature
  • Collision-resistant: No separate hash function needed
  • Side-channel resistant: Constant-time implementation
  • Small keys: 32 bytes each (public and private)

Security Considerations

  • Ed25519 does not support key recovery from signatures
  • Verify the full message, not a hash (Ed25519 hashes internally)
  • Public keys must be validated before use (check for low-order points)
  • Private keys should be stored encrypted at rest
  • Ed25519 is not yet approved for all NIST use cases (Ed448 is preferred for federal)

Validation Criteria

  • Key pair generation produces valid Ed25519 keys
  • Signature verification succeeds for valid message
  • Signature verification fails for tampered message
  • Signature verification fails for wrong public key
  • Deterministic: same input produces same signature
  • File signing and verification works correctly
  • Performance meets or exceeds RSA-3072