Implementing Digital Signatures with Ed25519
FreeSecurely sign and verify messages with Ed25519.
Free · Opens the source repo
What Implementing Digital Signatures with Ed25519 does
The Implementing Digital Signatures with Ed25519 skill provides a robust framework for integrating digital signatures into your applications using the Ed25519 algorithm. Ed25519 is known for its high performance and security, offering 128-bit security with compact 64-byte signatures and 32-byte keys. This skill guides users through the entire process of key-pair generation, signing messages, verifying signatures, and understanding the security trade-offs compared to traditional algorithms like RSA and ECDSA. It is particularly useful for developers and security professionals looking to enhance the integrity and authenticity of their systems.
This skill includes practical implementations for document signing, code signing, and API authentication, making it versatile for various applications in software development and cybersecurity. With key features like deterministic signatures, which eliminate the need for random nonces, and resistance to side-channel attacks, Ed25519 stands out as a modern choice for secure digital signatures. Users will also learn to establish security controls that align with compliance requirements and improve overall security architecture.
The skill is designed for those familiar with cryptography concepts and tools, providing a hands-on approach to building a simple code signing system and conducting performance comparisons with RSA and ECDSA. It emphasizes best practices for key management and signature validation, ensuring that users can implement Ed25519 securely and effectively. Overall, this skill is an essential resource for anyone looking to implement strong authentication and integrity checks in their systems.
When to use it
Use this skill when you need to add digital signatures to your applications or when conducting security assessments requiring Ed25519.
When not to use it
This skill may not be suitable if you require support for key recovery from signatures or if you need to comply with specific NIST use cases not covered by Ed25519.
What you can build with it
Document Signing
Implement Ed25519 to sign documents, ensuring their authenticity and integrity.
Code Signing
Use this skill to create a secure code signing system that verifies the integrity of software.
API Authentication
Integrate Ed25519 for authenticating API requests, providing a secure method for message verification.
How to install Implementing Digital Signatures with Ed25519
View source1. Install with the skills CLI
npx skills add mukul975/anthropic-cybersecurity-skills/implementing-digital-signatures-with-ed25519 --agent claude-code2. Or install it manually
Download the skill folder and drop it into ~/.claude/skills/ for all projects, or .claude/skills/ to scope it to one repo. Restart Claude Code so it picks up the new skill.
Anthropic's agentic coding CLI, and the reference implementation of Agent Skills. Drop a skill folder into ~/.claude/skills and Claude Code loads it automatically whenever a task matches the skill's description. Claude Code docs
Inside SKILL.md
Written by mukul975Implementing 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
Frequently asked questions about Implementing Digital Signatures with Ed25519
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