Initial public release: Nym-native anonymous submission system

End-to-end verified pipeline (browser -> HTTP relay -> Nym mixnet -> reader).
Client-side X25519+HKDF+AES-GCM-256, no-log blind relay, AGPL-3.0.

1 files changed, 111 insertions, 0 deletions

diff --git a/static/crypto.js b/static/crypto.js
new file mode 100644
index 0000000..63b395f
--- /dev/null
+++ b/static/crypto.js
@@ -0,0 +1,111 @@
+// NymDrop — client-side encryption via WebCrypto API.
+// No external libraries. Plaintext never leaves the browser.
+
+// Server's X25519 public key — replaced at deploy time.
+const NYMDROP_PUBKEY_HEX = "6aa99a672c48cb8eee65ddd5c5e5f8947a8d52d39a8b8eb4e11b15c87fe49038";
+
+async function hexToBytes(hex) {
+    const bytes = new Uint8Array(hex.length / 2);
+    for (let i = 0; i < hex.length; i += 2)
+        bytes[i / 2] = parseInt(hex.substr(i, 2), 16);
+    return bytes;
+}
+
+async function encryptPayload(plaintext) {
+    const serverPubBytes = await hexToBytes(NYMDROP_PUBKEY_HEX);
+
+    // Generate ephemeral X25519 keypair for this submission.
+    const ephemeral = await crypto.subtle.generateKey(
+        { name: "ECDH", namedCurve: "X25519" },
+        true,
+        ["deriveKey", "deriveBits"]
+    );
+
+    // Import server's X25519 public key.
+    const serverKey = await crypto.subtle.importKey(
+        "raw",
+        serverPubBytes,
+        { name: "ECDH", namedCurve: "X25519" },
+        false,
+        []
+    );
+
+    // ECDH key agreement → 32-byte shared secret.
+    const sharedBits = await crypto.subtle.deriveBits(
+        { name: "ECDH", public: serverKey },
+        ephemeral.privateKey,
+        256
+    );
+
+    // Derive AES-GCM-256 key via HKDF-SHA-256.
+    const hkdfKey = await crypto.subtle.importKey("raw", sharedBits, "HKDF", false, ["deriveKey"]);
+    const aesKey = await crypto.subtle.deriveKey(
+        {
+            name: "HKDF",
+            hash: "SHA-256",
+            salt: new Uint8Array(32),
+            info: new TextEncoder().encode("nymdrop-v1")
+        },
+        hkdfKey,
+        { name: "AES-GCM", length: 256 },
+        false,
+        ["encrypt"]
+    );
+
+    // Encrypt plaintext.
+    const iv = crypto.getRandomValues(new Uint8Array(12));
+    const ciphertext = await crypto.subtle.encrypt(
+        { name: "AES-GCM", iv },
+        aesKey,
+        new TextEncoder().encode(plaintext)
+    );
+
+    // Export ephemeral X25519 public key (32 bytes raw).
+    const ephemeralPubRaw = await crypto.subtle.exportKey("raw", ephemeral.publicKey);
+
+    // Packet layout: ephemeral_pub(32) + iv(12) + ciphertext
+    const packet = new Uint8Array(32 + 12 + ciphertext.byteLength);
+    packet.set(new Uint8Array(ephemeralPubRaw), 0);
+    packet.set(iv, 32);
+    packet.set(new Uint8Array(ciphertext), 44);
+
+    return packet;
+}
+
+document.getElementById("drop-form").addEventListener("submit", async (e) => {
+    e.preventDefault();
+    const status = document.getElementById("status");
+    status.className = "";
+    status.textContent = "Encrypting...";
+
+    try {
+        let plaintext = document.getElementById("message").value;
+
+        const fileInput = document.getElementById("file");
+        if (fileInput.files.length > 0) {
+            const fileBytes = await fileInput.files[0].arrayBuffer();
+            const fileB64 = btoa(String.fromCharCode(...new Uint8Array(fileBytes)));
+            plaintext += "\n---FILE:" + fileInput.files[0].name + "---\n" + fileB64;
+        }
+
+        const encrypted = await encryptPayload(plaintext);
+
+        const resp = await fetch("/submit", {
+            method: "POST",
+            headers: { "Content-Type": "application/octet-stream" },
+            body: encrypted,
+        });
+
+        if (resp.ok) {
+            document.getElementById("drop-form").reset();
+            document.getElementById("filename").textContent = "";
+            status.textContent = "Delivered. No record of this submission exists on the server.";
+        } else {
+            status.className = "error";
+            status.textContent = "Delivery failed. Try again.";
+        }
+    } catch (err) {
+        status.className = "error";
+        status.textContent = "Encryption failed: " + err.message;
+    }
+});