Ed25519 sign & verify
Sign a message with your Ed25519 private key, or verify a signature with the public key. Keys as PEM, hex, or base64; deterministic (RFC 8032). Runs in your browser — keys never leave your device.
About this tool
Ed25519 Sign & Verify does both halves of an Ed25519 signature in one place. Pick Sign to turn a message + your private key into a signature, or Verify to check a signature against a message and the signer's public key. Everything runs in your browser via WebAssembly — your keys and messages are never uploaded.
Ed25519 is EdDSA over Curve25519 (RFC 8032): fast, 32-byte keys, 64-byte
signatures, and used by SSH, OpenPGP, JWT (EdDSA), and TLS.
Worked example
Sign the single byte 0x72 with the RFC 8032 test key. Choose Sign, set
Message to 72, Message encoding to Hex, and paste the raw private
key:
key = 4ccd089b28ff96da9db6c346ec114e0f5b8a319f35aba624da8cf6ed4fb8a6fb
You get back the deterministic signature and the derived public key:
signature (hex): 92a009a9f0d4cab8720e820b5f642540a2b27b5416503f8fb3762223ebdb69da
085ac1e43e15996e458f3613d0f11d8c387b2eaeb4302aeeb00d291612bb0c00
public key (hex): 3d4017c3e843895a92b70aa74d1b7ebc9c982ccf2ec4968cc0cd55f12af4660c
Switch to Verify, keep the same message, paste that public key into the
key box and the signature into the signature box, and you get valid: true.
Options
- Operation — Sign (message + private key → signature) or Verify (message + public key + signature → valid / not valid).
- Message encoding — how the message box is read into bytes: UTF-8 text (default), Hex, or Base64 (for signing binary payloads).
- Key — for signing, an Ed25519 private key; for verifying, the
public key. Accepts PEM (
-----BEGIN PRIVATE KEY-----PKCS#8 /-----BEGIN PUBLIC KEY-----SPKI), or a raw 32-byte key as hex or base64. A private key may also be a 64-byteseed || publickeypair. - Signature — only for verify: the raw 64-byte signature as hex or base64.
Deterministic signatures
Ed25519 is deterministic by design (RFC 8032): the nonce is derived from the key and message, so signing the same message with the same key always produces the same signature. There is no RNG and no repeated-nonce risk.
Limits & edge cases
- Keys are Ed25519 only — this is not ECDSA (P-256/P-384) or RSA. A raw key must decode to exactly 32 bytes (public / private seed) or 64 bytes (private keypair); signatures must decode to 64 bytes.
- Verifying a signature that simply doesn't match returns
valid: false— that's a normal result, not an error. Errors are reserved for malformed keys or signatures. - Whitespace inside hex/base64 is ignored, so space-separated hex pastes fine.
FAQ
What key formats can I paste?
For signing: an Ed25519 private key as PKCS#8 PEM (-----BEGIN PRIVATE KEY-----), or the raw 32-byte seed as hex or base64 (a 64-byte seed || public keypair also works). For verifying: the public key as SPKI PEM (-----BEGIN PUBLIC KEY-----) or the raw 32-byte point as hex or base64. The tool auto-detects hex vs base64 by length.
Why is the signature the same every time I sign?
That's expected. Ed25519 signatures are deterministic (RFC 8032) — the per-signature nonce is derived from the private key and message rather than a random number, so the same key + message always yields the same 64-byte signature. It removes the catastrophic key-leak risk that a repeated random nonce causes in ECDSA.
Verify says "valid: false" — what went wrong?
The signature doesn't match the message under that public key. Common causes: the message text or message encoding differs from what was signed (a trailing newline counts), the signature belongs to a different key, or you pasted the wrong public key. Double-check that the message bytes and public key are exactly the signer's.
Is this the same as ECDSA, RSA, or SSH signing?
No. Ed25519 is EdDSA over Curve25519 — a different scheme from ECDSA (NIST P-256/P-384) and RSA. It's the algorithm behind modern ssh-ed25519 keys and JWT's EdDSA, but the raw signature here is not an SSH or PGP wire signature — it's the bare 64-byte Ed25519 signature.
Do my keys or messages leave the browser?
No. Signing and verifying run locally in WebAssembly; nothing is sent to a server. Still, treat any pasted production private key with care and prefer test keys where you can.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool ed25519-sign-verify "..."New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/ed25519-sign-verify/?operation=sign&message=The%20message%20to%20sign%20or%20verify&message_encoding=utf8&key=-----BEGIN%20PRIVATE%20KEY-----%0A...%0A-----END%20PRIVATE%20KEY-----%20%20%20%C2%B7%20%20%20or%20raw%2032-byte%20key%20as%20hex%2Fbase64&signature=hex%20or%20base64%20signature%20%E2%80%94%20required%20when%20verifyingMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.