Create ed25519.js

Author: Web4application

Webapi/web-crypto/sign-verify/ed25519.js

@@ -0,0 +1,74 @@
+(() => {
+  /*
+  Store the calculated signature here, so we can verify it later.
+  */
+  let signature;
+
+  /*
+  Fetch the contents of the "message" textbox, and encode it
+  in a form we can use for sign operation.
+  */
+  function getMessageEncoding() {
+    const messageBox = document.querySelector("#ed25519-message");
+    let message = messageBox.value;
+    let enc = new TextEncoder();
+    return enc.encode(message);
+  }
+
+  /*
+  Get the encoded message-to-sign, sign it and display a representation
+  of the first part of it in the "signature" element.
+  */
+  async function signMessage(privateKey) {
+    const signatureValue = document.querySelector(".ed25519 .signature-value");
+    signatureValue.classList.remove("valid", "invalid");
+
+    let encoded = getMessageEncoding();
+    signature = await window.crypto.subtle.sign("Ed25519", privateKey, encoded);
+
+    signatureValue.classList.add("fade-in");
+    signatureValue.addEventListener("animationend", () => {
+      signatureValue.classList.remove("fade-in");
+    });
+    let buffer = new Uint8Array(signature, 0, 5);
+    signatureValue.textContent = `${buffer}...[${signature.byteLength} bytes total]`;
+  }
+
+  /*
+  Fetch the encoded message-to-sign and verify it against the stored signature.
+  * If it checks out, set the "valid" class on the signature.
+  * Otherwise set the "invalid" class.
+  */
+  async function verifyMessage(publicKey) {
+    const signatureValue = document.querySelector(".ed25519 .signature-value");
+    signatureValue.classList.remove("valid", "invalid");
+
+    let encoded = getMessageEncoding();
+    let result = await window.crypto.subtle.verify(
+      "Ed25519",
+      publicKey,
+      signature,
+      encoded
+    );
+
+    signatureValue.classList.add(result ? "valid" : "invalid");
+  }
+
+  /*
+  Generate a sign/verify key, then set up event listeners
+  on the "Sign" and "Verify" buttons.
+  */
+  window.crypto.subtle
+    .generateKey("Ed25519", true, ["sign", "verify"])
+    .then((keyPair) => {
+      const signButton = document.querySelector(".ed25519 .sign-button");
+      signButton.addEventListener("click", () => {
+        signMessage(keyPair.privateKey);
+      });
+
+      const verifyButton = document.querySelector(".ed25519 .verify-button");
+      verifyButton.addEventListener("click", () => {
+        verifyMessage(keyPair.publicKey);
+      });
+    });
+})();