하나의 공개 키로 여러 계정에 로그인할 수 있도록 구현

src/lib/modules/crypto.ts

@@ -0,0 +1,50 @@
+export type RSAKeyType = "public" | "private";
+
+export const generateRSAKeyPair = async () => {
+  const keyPair = await window.crypto.subtle.generateKey(
+    {
+      name: "RSA-OAEP",
+      modulusLength: 4096,
+      publicExponent: new Uint8Array([1, 0, 1]),
+      hash: "SHA-256",
+    } satisfies RsaHashedKeyGenParams,
+    true,
+    ["encrypt", "decrypt"],
+  );
+  return keyPair;
+};
+
+export const makeRSAKeyNonextractable = async (key: CryptoKey, type: RSAKeyType) => {
+  const format = type === "public" ? "spki" : "pkcs8";
+  const keyUsage = type === "public" ? "encrypt" : "decrypt";
+  return await window.crypto.subtle.importKey(
+    format,
+    await window.crypto.subtle.exportKey(format, key),
+    {
+      name: "RSA-OAEP",
+      hash: "SHA-256",
+    } satisfies RsaHashedImportParams,
+    false,
+    [keyUsage],
+  );
+};
+
+export const exportRSAKeyToBase64 = async (key: CryptoKey, type: RSAKeyType) => {
+  const exportedKey = await window.crypto.subtle.exportKey(
+    type === "public" ? "spki" : "pkcs8",
+    key,
+  );
+  return btoa(String.fromCharCode(...new Uint8Array(exportedKey)));
+};
+
+export const decryptRSACiphertext = async (ciphertext: string, privateKey: CryptoKey) => {
+  const ciphertextBuffer = Uint8Array.from(atob(ciphertext), (c) => c.charCodeAt(0));
+  const plaintext = await window.crypto.subtle.decrypt(
+    {
+      name: "RSA-OAEP",
+    } satisfies RsaOaepParams,
+    privateKey,
+    ciphertextBuffer,
+  );
+  return btoa(String.fromCharCode(...new Uint8Array(plaintext)));
+};