1 files changed, 63 insertions, 0 deletions
diff --git a/std/jwt/_signature.ts b/std/jwt/_signature.ts
new file mode 100644
index 000000000..81c1309d1
--- /dev/null
+++ b/std/jwt/_signature.ts
@@ -0,0 +1,63 @@
+import type { Algorithm } from "./_algorithm.ts";
+import { HmacSha256 } from "../hash/sha256.ts";
+import { HmacSha512 } from "../hash/sha512.ts";
+import { encode as convertUint8ArrayToBase64url } from "../encoding/base64url.ts";
+import { decodeString as convertHexToUint8Array } from "../encoding/hex.ts";
+
+export function convertHexToBase64url(input: string): string {
+  return convertUint8ArrayToBase64url(convertHexToUint8Array(input));
+}
+
+function encrypt(
+  algorithm: Algorithm,
+  key: string,
+  message: string,
+): string {
+  switch (algorithm) {
+    case "none":
+      return "";
+    case "HS256":
+      return new HmacSha256(key).update(message).toString();
+    case "HS512":
+      return new HmacSha512(key).update(message).toString();
+    default:
+      throw new RangeError(
+        `The algorithm of '${algorithm}' in the header is not supported.`,
+      );
+  }
+}
+
+/**
+ * Create a signature
+ * @param algorithm
+ * @param key
+ * @param input
+ */
+export async function create(
+  algorithm: Algorithm,
+  key: string,
+  input: string,
+): Promise<string> {
+  return convertHexToBase64url(await encrypt(algorithm, key, input));
+}
+
+/**
+ * Verify a signature
+ * @param signature
+ * @param key
+ * @param alg
+ * @param signingInput
+ */
+export async function verify({
+  signature,
+  key,
+  algorithm,
+  signingInput,
+}: {
+  signature: string;
+  key: string;
+  algorithm: Algorithm;
+  signingInput: string;
+}): Promise<boolean> {
+  return signature === (await encrypt(algorithm, key, signingInput));
+}