diff --git a/src/browser/tests/crypto.html b/src/browser/tests/crypto.html
index 74c30f02..8f477535 100644
--- a/src/browser/tests/crypto.html
+++ b/src/browser/tests/crypto.html
@@ -47,6 +47,54 @@
   // }
 </script>
 
+<script id=SubtleCrypto>
+  testing.async(async () => {
+    let key = await crypto.subtle.generateKey(
+      {
+        name: "HMAC",
+        hash: { name: "SHA-512" },
+      },
+      true,
+      ["sign", "verify"],
+    );
+
+    //const raw = crypto.subtle.exportKey("adv", key).catch(err => console.warn(err));
+    //testing.expectEqual(128, raw.byteLength);
+
+    const encoder = new TextEncoder();
+
+    const signature = await crypto.subtle.sign(
+      "HMAC",
+      key,
+      encoder.encode("Hello, world!")
+    );
+
+    const result = await window.crypto.subtle.verify(
+      { name: "HMAC" },
+      key,
+      signature,
+      encoder.encode("Hello, world!")
+    );
+
+    testing.expectEqual(true, true);
+  });
+</script>
+
+<script id=X25519>
+  testing.async(async () => {
+    const { privateKey, publicKey } = await crypto.subtle.generateKey(
+      { name: "X25519" },
+      true,
+      ["deriveKey", "deriveBits"],
+    );
+
+    console.warn(privateKey);
+    console.warn(publicKey);
+
+    testing.expectEqual(true, true);
+  });
+</script>
+
 <!-- <script id="randomUUID">
   const uuid = crypto.randomUUID();
   testing.expectEqual('string', typeof uuid);
diff --git a/src/crypto.zig b/src/crypto.zig
index 99762a82..31609c42 100644
--- a/src/crypto.zig
+++ b/src/crypto.zig
@@ -26,3 +26,9 @@ pub extern fn HMAC(
     out: [*]u8,
     out_len: *c_uint,
 ) ?[*]u8;
+
+pub const X25519_PRIVATE_KEY_LEN = 32;
+pub const X25519_PUBLIC_VALUE_LEN = 32;
+pub const X25519_SHARED_KEY_LEN = 32;
+
+pub extern fn X25519_keypair(out_public_value: *[32]u8, out_private_key: *[32]u8) void;