+ create user with public/private key

+ sign and verify votes and prevent unverified updates

server/utils/crypto.ts

@@ -0,0 +1,86 @@
+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) {
+        // 1. Reconstruct the exact data state the user signed
+        // We need the array exactly as it was when they pushed their vote
+        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 bytes = Buffer.from(keyStr, 'base64');
+
+  // 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,
+    {
+      name: "RSASSA-PKCS1-v1_5",
+      hash: "SHA-256",
+    },
+    true, // extractable (set to false if you want to lock it in memory)
+    usages
+  );
+};

server/utils/types.ts

@@ -0,0 +1,36 @@
+export interface PollProps {
+    userid: string | undefined,
+    activePollId: string,
+    pollData: PollData,
+    addOption: (name: string) => void,
+    vote: (optionName: string) => void
+}
+
+export interface PollListProps {
+    userid: string | undefined,
+}
+
+export interface PollData extends Record<string, SignedData<VoteData>[]> {
+}
+
+export interface SignedData<T> {
+    data: T,
+    signature: string
+}
+
+export interface VoteData {
+    userid: string,
+    timestamp: string
+}
+
+export interface OptionData {
+    userid: string,
+    timestamp: string,
+    optionName: string
+}
+
+export interface UserData {
+    userid: string,
+    private_key: CryptoKey | undefined,
+    public_key: CryptoKey | undefined
+}