implementing-digital-signatures-with-ed25519
Has your agent implement secure digital signatures using the Ed25519 algorithm, ensuring data authenticity and integrity.
What it does
This tool helps create secure digital signatures using a method called Ed25519. It allows you to confirm if a message or file is authentic and hasn't been altered.
When to use it
- ✓When needing to ensure the authenticity of important documents.
- ✓When wanting to verify if a program or file hasn't been modified.
- ✓When setting up security systems to protect information.
Example of what to ask your AI
“How can I create a digital signature for this document using Ed25519?”
Want more? Open the sections below.
How to use
The easiest way: copy the message below and paste it into Claude, ChatGPT, Cursor or any AI. It reads the skill and follows the instructions.
Skill link
Ready-to-paste message
How it works
It generates a key pair (one public, one private) for signing. The private key creates the signature, and the public key verifies if it's valid. This ensures the message came from the claimed sender and hasn't been changed.
Installation
Easiest way: copy the skill link and paste it into Claude, ChatGPT or Cursor asking it to follow the instructions.
In the terminal (Claude Code, Codex, Cursor), in your project folder:
npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill implementing-digital-signatures-with-ed25519Or download just the file:
curl -L https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/main/skills/implementing-digital-signatures-with-ed25519/SKILL.md -o SKILL.mdTechnical content (original SKILL.md)
Original text by the author, straight from GitHub.
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
FAQ
What is a digital signature?
It's like a seal of authenticity for digital data. It guarantees the information is original and hasn't been tampered with.
Why use Ed25519?
It's a modern and fast method for creating digital signatures, often more secure and efficient than older methods like RSA.
What are public and private keys?
The private key is secret and used to create the signature. The public key can be shared and is used to verify the signature, confirming its validity.
Details
Original description by the author
Implements digital signatures using the Ed25519 algorithm (Curve25519), covering key-pair generation, signing, signature verification, and security tradeoffs versus RSA and ECDSA. Use when adding message or artifact signing and authentication-integrity checks to a system, or when advising on Ed25519 key properties and validation criteria.
Popularity
- GitHub stars
- 35k
- Ranking position
- #5866
- License
- Apache-2.0
- Updated
- 8/31/2026
Comments
- …
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