add vote uniqueness, public key caching, relative poll timeframe, auth/rate limiting, modern UI styling, and error handling

server/utils/crypto.ts

@@ -0,0 +1,89 @@
+import { SignedData, VoteData } from "./types";
+/**
+ * Gets the WebCrypto API regardless of environment (Node vs Browser)
+ */
+const getCrypto = () => {
+  return (globalThis as any).crypto;
+};
+
+export const verifyVote = async (data: any, signatureStr: string, publicKey: CryptoKey) => {
+  const encoder = new TextEncoder();
+  const encodedData = encoder.encode(JSON.stringify(data));
+  
+  // Convert Base64 back to Uint8Array
+  const signature = Uint8Array.from(atob(signatureStr), c => c.charCodeAt(0));
+
+  return await getCrypto().subtle.verify(
+    "RSASSA-PKCS1-v1_5",
+    publicKey,
+    signature,
+    encodedData
+  );
+};
+
+/**
+ * Verifies a specific vote within an array of votes by 
+ * reconstructing the "signed state" at that point in time.
+ */
+export const verifyChainedVote = async (
+    voteData: SignedData<VoteData>[], 
+    index: number,
+    pubKey: CryptoKey
+) => {
+    const voteToVerify = voteData[index];
+    console.log("Verifying vote: " + voteToVerify)
+    if(voteToVerify) {
+       
+        const historicalState = voteData.slice(0, index + 1).map((v, i) => {
+            if (i === index) {
+                // For the current vote, the signature must be empty string
+                // because it wasn't signed yet when passed to signVote
+                return { ...v, signature: "" };
+            }
+            return v;
+        });
+
+        try {
+            // 3. Verify: Does this historicalState match the signature?
+            return await verifyVote(historicalState, voteToVerify.signature, pubKey);
+        } catch (err) {
+            console.error("Verification failed")
+            console.error(err);
+            return false;
+        }
+    }
+    console.error("Vote is undefined or null");
+    return false;
+};
+
+
+/**
+ * Converts a Base64 string back into a usable CryptoKey object
+ * @param keyStr The Base64 string (without PEM headers)
+ * @param type 'public' or 'private'
+ */
+export const stringToCryptoKey = async (keyStr: string, type: 'public' | 'private'): Promise<CryptoKey> => {
+  // 1. Convert Base64 string to a Uint8Array (binary)
+  const binaryString = Buffer.from(keyStr, 'base64').toString('binary');
+  const bytes = new Uint8Array(binaryString.length);
+  for (let i = 0; i < binaryString.length; i++) {
+    bytes[i] = binaryString.charCodeAt(i);
+  }
+
+  // 2. Identify the format based on the key type
+  // Public keys usually use 'spki', Private keys use 'pkcs8'
+  const format = type === 'public' ? 'spki' : 'pkcs8';
+  const usages: KeyUsage[] = type === 'public' ? ['verify'] : ['sign'];
+
+  // 3. Import the key
+  return await getCrypto().subtle.importKey(
+    format,
+    bytes.buffer,
+    {
+      name: "RSASSA-PKCS1-v1_5",
+      hash: "SHA-256",
+    },
+    true, // extractable (set to false if you want to lock it in memory)
+    usages
+  );
+};