diff --git a/.gitignore b/.gitignore
index 6035f8f..6d5e14b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,3 @@
 /target
 .DS_Store
-*.img
\ No newline at end of file
+*.img
diff --git a/Cargo.lock b/Cargo.lock
index 9ca30b3..b39c030 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -291,7 +291,13 @@ version = "0.1.0"
 name = "gatekeeper"
 version = "0.1.0"
 dependencies = [
+ "driver-block-virtio",
+ "driver-rng-virtio",
  "keystore",
+ "libkos",
+ "port-block-device",
+ "port-entropy",
+ "types",
  "zeroize",
 ]
 
diff --git a/Makefile b/Makefile
index 47f1b9e..1104e09 100644
--- a/Makefile
+++ b/Makefile
@@ -55,11 +55,17 @@ build:
 		-p init -p echo -p sleep -p snake \
 		-p display-qemu -p input-qemu -p storage-qemu \
 		-p log-server -p permission-manager -p session-server -p smptest -p spawntest -p hello \
-		-p terminal-server -p shell -p cat -p ls -p counter
+		-p terminal-server -p shell -p cat -p ls -p counter -p gatekeeper
 	cargo build --target $(RISCV_TARGET) --release -p adapter-riscv
 
+# The keystore holds the owner's sealed keys: made once, never rebuilt.
+KEYS_IMG ?= keys.img
+QEMU_KEYS = -drive file=$(KEYS_IMG),if=none,format=raw,id=ks -device virtio-blk-device,drive=ks \
+	-device virtio-rng-device
+
 image: build
 	scripts/make-disk-image.sh
+	[ -f $(KEYS_IMG) ] || truncate -s 64K $(KEYS_IMG)
 
 # Boots a test image (normal image + bin/smptest) on $(SMP) harts; init runs
 # the SMP self-test and halts. Passes only on "SMPTEST PASS".
@@ -75,13 +81,13 @@ run-disk: image
 	qemu-system-riscv64 -machine virt -smp $(SMP) -nographic -bios default \
 		-kernel $(KERNEL_BIN) \
 		-drive file=boot.img,if=none,format=raw,id=hd0 \
-		-device virtio-blk-device,drive=hd0
+		-device virtio-blk-device,drive=hd0 $(QEMU_KEYS)
 
 run-gui: image
 	qemu-system-riscv64 -machine virt -smp $(SMP) -bios default \
 		-kernel $(KERNEL_BIN) \
 		-drive file=boot.img,if=none,format=raw,id=hd0 \
-		-device virtio-blk-device,drive=hd0 \
+		-device virtio-blk-device,drive=hd0 $(QEMU_KEYS) \
 		-device virtio-gpu-device \
 		-device virtio-keyboard-device \
 		-serial stdio
diff --git a/crates/apps/spawntest/src/main.rs b/crates/apps/spawntest/src/main.rs
index 7eed431..8cb4476 100644
--- a/crates/apps/spawntest/src/main.rs
+++ b/crates/apps/spawntest/src/main.rs
@@ -57,6 +57,8 @@ fn run_hello(fs: &mut Storage, died: CapSlot, grant: Option<CapSlot>) -> Result<
 
 /// A file written through storage, which the host then checks with e2fsck.
 fn write_a_file(fs: &mut Storage) -> Result<(), &'static str> {
+    // Left by an earlier boot of the same disk.
+    let _ = fs.delete(b"selftest.txt");
     let h = fs.create(b"selftest.txt").map_err(|_| "cannot create a file")?;
     if fs.write(h, NOTE) != Ok(NOTE.len()) {
         return Err("short write");
diff --git a/crates/drivers/block/virtio/src/lib.rs b/crates/drivers/block/virtio/src/lib.rs
index a7578fb..f6eda75 100644
--- a/crates/drivers/block/virtio/src/lib.rs
+++ b/crates/drivers/block/virtio/src/lib.rs
@@ -8,9 +8,11 @@ use port_block_device::{BlockDevice, SectorId};
 use types::address::{ByteOffset, PhysicalAddress, VirtualAddress};
 use types::bounded::PageCount;
 
-const MMIO_VA: VirtualAddress = VirtualAddress::from_raw(0x20000);
-const VQUEUE_VA: VirtualAddress = VirtualAddress::from_raw(0x21000);
-const REQ_HDR_VA: VirtualAddress = VirtualAddress::from_raw(0x23000);
+/// Drivers map their devices in the device window (0x01D0_0000 up, 64 KiB
+/// each), clear of program images and heaps.
+const MMIO_VA: VirtualAddress = VirtualAddress::from_raw(0x01D0_0000);
+const VQUEUE_VA: VirtualAddress = VirtualAddress::from_raw(0x01D0_1000);
+const REQ_HDR_VA: VirtualAddress = VirtualAddress::from_raw(0x01D0_3000);
 const SECTOR_SIZE: usize = 512;
 
 pub struct VirtioBlockDevice {
diff --git a/crates/drivers/framebuffer/virtio/src/lib.rs b/crates/drivers/framebuffer/virtio/src/lib.rs
index 4bd50ae..9113a8e 100644
--- a/crates/drivers/framebuffer/virtio/src/lib.rs
+++ b/crates/drivers/framebuffer/virtio/src/lib.rs
@@ -10,9 +10,11 @@ use types::address::{ByteOffset, PhysicalAddress, VirtualAddress};
 use types::bounded::PageCount;
 use types::display::{Color, Dimension, ScreenCoord};
 
-const GPU_MMIO_VA: VirtualAddress = VirtualAddress::from_raw(0x20000);
-const VQUEUE_VA: VirtualAddress = VirtualAddress::from_raw(0x21000);
-const CMDBUF_VA: VirtualAddress = VirtualAddress::from_raw(0x23000);
+/// Drivers map their devices in the device window (0x01D0_0000 up, 64 KiB
+/// each), clear of program images and heaps.
+const GPU_MMIO_VA: VirtualAddress = VirtualAddress::from_raw(0x01D2_0000);
+const VQUEUE_VA: VirtualAddress = VirtualAddress::from_raw(0x01D2_1000);
+const CMDBUF_VA: VirtualAddress = VirtualAddress::from_raw(0x01D2_3000);
 const FB_VA: VirtualAddress = VirtualAddress::from_raw(0x100000);
 const FB_BPP: usize = 4;
 /// Pixels converted and stored per run.
diff --git a/crates/drivers/input/uart/src/lib.rs b/crates/drivers/input/uart/src/lib.rs
index a2081c8..3c57e62 100644
--- a/crates/drivers/input/uart/src/lib.rs
+++ b/crates/drivers/input/uart/src/lib.rs
@@ -5,7 +5,9 @@ use libkos::Window;
 use port_input_device::{InputDevice, InputEvent, Key};
 use types::address::{ByteOffset, VirtualAddress};
 
-const UART_VA: VirtualAddress = VirtualAddress::from_raw(0x20000);
+/// Drivers map their devices in the device window (0x01D0_0000 up, 64 KiB
+/// each), clear of program images and heaps.
+const UART_VA: VirtualAddress = VirtualAddress::from_raw(0x01D4_0000);
 const UART_RBR: ByteOffset = ByteOffset::new(0);
 const UART_IER_OFFSET: ByteOffset = ByteOffset::new(1);
 const UART_LSR_OFFSET: ByteOffset = ByteOffset::new(5);
diff --git a/crates/drivers/input/virtio/src/lib.rs b/crates/drivers/input/virtio/src/lib.rs
index 89844c8..758d454 100644
--- a/crates/drivers/input/virtio/src/lib.rs
+++ b/crates/drivers/input/virtio/src/lib.rs
@@ -10,9 +10,11 @@ use port_input_device::{InputDevice, InputEvent};
 use types::address::{ByteOffset, PhysicalAddress, VirtualAddress};
 use types::bounded::PageCount;
 
-const INPUT_MMIO_VA: VirtualAddress = VirtualAddress::from_raw(0x25000);
-const VQUEUE_VA: VirtualAddress = VirtualAddress::from_raw(0x26000);
-const EVBUF_VA: VirtualAddress = VirtualAddress::from_raw(0x28000);
+/// Drivers map their devices in the device window (0x01D0_0000 up, 64 KiB
+/// each), clear of program images and heaps.
+const INPUT_MMIO_VA: VirtualAddress = VirtualAddress::from_raw(0x01D1_0000);
+const VQUEUE_VA: VirtualAddress = VirtualAddress::from_raw(0x01D1_1000);
+const EVBUF_VA: VirtualAddress = VirtualAddress::from_raw(0x01D1_3000);
 
 const QUEUE_SIZE: usize = 32;
 const EVENT_SIZE: usize = 8;
diff --git a/crates/drivers/rng/virtio/src/lib.rs b/crates/drivers/rng/virtio/src/lib.rs
index 791da2f..d740c5a 100644
--- a/crates/drivers/rng/virtio/src/lib.rs
+++ b/crates/drivers/rng/virtio/src/lib.rs
@@ -10,9 +10,11 @@ use port_entropy::Entropy;
 use types::address::{ByteOffset, VirtualAddress};
 use types::bounded::PageCount;
 
-const MMIO_VA: VirtualAddress = VirtualAddress::from_raw(0x2A000);
-const VQUEUE_VA: VirtualAddress = VirtualAddress::from_raw(0x2B000);
-const BUFFER_VA: VirtualAddress = VirtualAddress::from_raw(0x2D000);
+/// Drivers map their devices in the device window (0x01D0_0000 up, 64 KiB
+/// each), clear of program images and heaps.
+const MMIO_VA: VirtualAddress = VirtualAddress::from_raw(0x01D3_0000);
+const VQUEUE_VA: VirtualAddress = VirtualAddress::from_raw(0x01D3_1000);
+const BUFFER_VA: VirtualAddress = VirtualAddress::from_raw(0x01D3_3000);
 /// Asked for at most this much at a time.
 const CHUNK: usize = 256;
 
diff --git a/crates/init/src/devices.rs b/crates/init/src/devices.rs
index fdedd28..39d4fa5 100644
--- a/crates/init/src/devices.rs
+++ b/crates/init/src/devices.rs
@@ -1,8 +1,9 @@
 //! Finds the board's devices (`types::bootinfo`): disk, GPU, and keyboard
 //! (or the UART when there is none).
 
+use hw_virtio::block::CONFIG_CAPACITY;
 use hw_virtio::mmio::{
-    DEVICE_ID_BLOCK, DEVICE_ID_GPU, DEVICE_ID_INPUT, MAGIC, REG_DEVICE_ID, REG_MAGIC,
+    DEVICE_ID_BLOCK, DEVICE_ID_GPU, DEVICE_ID_INPUT, DEVICE_ID_RNG, MAGIC, REG_DEVICE_ID, REG_MAGIC,
 };
 use libkos::device::{self, Device};
 use libkos::syscall;
@@ -19,8 +20,14 @@ pub struct Devices {
     pub disk: Device,
     pub gpu: Device,
     pub input: Device,
+    /// The gatekeeper's: a small disk of its own for the key slots.
+    pub keystore: Device,
+    pub random: Device,
 }
 
+/// A block device this small (1 MiB) is the keystore, not the disk.
+const KEYSTORE_MAX_SECTORS: u64 = 2048;
+
 fn slot(raw: u64) -> Option<CapSlot> {
     if raw == NO_SLOT {
         return None;
@@ -28,21 +35,30 @@ fn slot(raw: u64) -> Option<CapSlot> {
     CapSlot::new(u8::try_from(raw).ok()?)
 }
 
-/// The virtio device id behind `region`, 0 for an empty slot. Read through
-/// a copy of the capability, mapped only while looking and then dropped,
-/// which unmaps it.
-fn virtio_id(region: CapSlot) -> u32 {
+/// The virtio device id behind `region` (0 for an empty slot) and, for a
+/// block device, its size in sectors. Read through a copy of the
+/// capability, mapped only while looking and then dropped, which unmaps it.
+fn virtio_id(region: CapSlot) -> (u32, u64) {
     let perms = PermissionSet::empty().with(Permission::Read).with(Permission::Write);
     let Ok(copy) = syscall::mint(region, Badge::NONE, perms) else {
-        return 0;
+        return (0, 0);
     };
     let id = match device::map_mmio(copy, PROBE_VA) {
         // The registers stay mapped until the drop below.
         Ok(regs) => match regs.read::<u32>(REG_MAGIC) == MAGIC {
-            true => regs.read(REG_DEVICE_ID),
-            false => 0,
+            true => {
+                let id = regs.read(REG_DEVICE_ID);
+                let size = match id {
+                    DEVICE_ID_BLOCK => {
+                        regs.read::<u32>(CONFIG_CAPACITY) as u64 | (regs.read::<u32>(CONFIG_CAPACITY + 4) as u64) << 32
+                    }
+                    _ => 0,
+                };
+                (id, size)
+            }
+            false => (0, 0),
         },
-        Err(_) => 0,
+        Err(_) => (0, 0),
     };
     syscall::drop_cap(copy);
     id
@@ -74,7 +90,13 @@ pub fn console() -> Option<CapSlot> {
 /// Sorts the board's devices out.
 pub fn discover() -> Devices {
     let info = boot_info();
-    let mut found = Devices { disk: Device::NONE, gpu: Device::NONE, input: Device::NONE };
+    let mut found = Devices {
+        disk: Device::NONE,
+        gpu: Device::NONE,
+        input: Device::NONE,
+        keystore: Device::NONE,
+        random: Device::NONE,
+    };
     let mut uart = Device::NONE;
     for d in info.devices() {
         let Some(region) = slot(d.region_slot) else {
@@ -84,9 +106,11 @@ pub fn discover() -> Devices {
         let place = match d.kind {
             KIND_UART_16550 => &mut uart,
             KIND_VIRTIO => match virtio_id(region) {
-                DEVICE_ID_BLOCK => &mut found.disk,
-                DEVICE_ID_GPU => &mut found.gpu,
-                DEVICE_ID_INPUT => &mut found.input,
+                (DEVICE_ID_BLOCK, size) if size <= KEYSTORE_MAX_SECTORS => &mut found.keystore,
+                (DEVICE_ID_BLOCK, _) => &mut found.disk,
+                (DEVICE_ID_GPU, _) => &mut found.gpu,
+                (DEVICE_ID_INPUT, _) => &mut found.input,
+                (DEVICE_ID_RNG, _) => &mut found.random,
                 _ => continue,
             },
             _ => continue,
diff --git a/crates/init/src/launch.rs b/crates/init/src/launch.rs
index 60b7bfe..823a0ae 100644
--- a/crates/init/src/launch.rs
+++ b/crates/init/src/launch.rs
@@ -110,8 +110,12 @@ impl<'a> Launcher<'a> {
             if let Some(free) = self.served.iter_mut().find(|s| s.is_none()) {
                 *free = Some((p.name, ep));
             }
-            if let Some(device) = p.device {
-                note = self.give(device, ep);
+            for device in p.devices {
+                note = self.give(*device, ep);
+            }
+            if p.unlocks {
+                unlock(ep)?;
+                note = ", the owner is in";
             }
             if console.is_some() {
                 hand_over_console(ep);
@@ -139,6 +143,8 @@ impl<'a> Launcher<'a> {
         let (dev, given, none): (BoardDevice, _, _) = match device {
             Device::Gpu => (self.devices.gpu, ", gpu handed over", ", no gpu"),
             Device::Input => (self.devices.input, ", input device handed over", ", no input device"),
+            Device::Keystore => (self.devices.keystore, ", keystore handed over", ", no keystore"),
+            Device::Random => (self.devices.random, ", randomness handed over", ", no randomness"),
         };
         match libkos::device::give_device(ep, dev).is_ok() && dev.mmio.is_some() {
             true => given,
@@ -147,6 +153,23 @@ impl<'a> Launcher<'a> {
     }
 }
 
+/// Waits for the gatekeeper behind `ep` to authenticate the owner, then
+/// passes the master key on to storage, which alone keeps it.
+fn unlock(ep: CapSlot) -> Result<(), &'static str> {
+    use types::gatekeeper::{KEY, UNLOCK, reply};
+    match syscall::request(ep, [UNLOCK, 0, 0, 0]) {
+        Ok([reply::OK, ..]) => {}
+        _ => return Err("the gatekeeper could not unlock"),
+    }
+    let mut key = syscall::request(ep, [KEY, 0, 0, 0]).map_err(|_| "the gatekeeper gave no key")?;
+    let given = [0, 1].iter().all(|&half| {
+        let words = [types::storage::op::SET_KEY, half, key[half * 2], key[half * 2 + 1]];
+        syscall::request(crate::STORAGE_EP, words).is_ok_and(|r| r[0] == types::storage::reply::OK)
+    });
+    key.fill(0);
+    if given { Ok(()) } else { Err("storage would not take the key") }
+}
+
 /// From here on init prints through the log server, like everyone else,
 /// and holds no console of its own.
 fn hand_over_console(log: CapSlot) {
diff --git a/crates/init/src/lib.rs b/crates/init/src/lib.rs
index 4fbf816..2fd98bc 100644
--- a/crates/init/src/lib.rs
+++ b/crates/init/src/lib.rs
@@ -80,6 +80,11 @@ fn launch_all(launcher: &mut launch::Launcher, programs: &[manifest::Program]) {
         libkos::print!("init: loading {}... ", p.name);
         match launcher.launch(p) {
             Ok(note) => libkos::println!("ok{}", note),
+            // Without the owner, nothing that touches user data may start.
+            Err(why) if p.unlocks => {
+                libkos::println!("STOP ({})", why);
+                idle();
+            }
             Err(why) => libkos::println!("SKIP ({})", why),
         }
     }
diff --git a/crates/init/src/manifest.rs b/crates/init/src/manifest.rs
index 687776e..32751b9 100644
--- a/crates/init/src/manifest.rs
+++ b/crates/init/src/manifest.rs
@@ -7,6 +7,8 @@ use types::budget::Limits;
 pub enum Device {
     Gpu,
     Input,
+    Keystore,
+    Random,
 }
 
 /// A storage grant: a folder (or the whole disk, `b""`) and whether it may
@@ -23,7 +25,11 @@ pub struct Program {
     pub limits: Limits,
     /// Serves an endpoint, which it finds in slot 0.
     pub serves: bool,
-    pub device: Option<Device>,
+    /// Handed over in this order, after it starts.
+    pub devices: &'static [Device],
+    /// Authenticates the owner: init waits for the master key before
+    /// starting anything that touches user data.
+    pub unlocks: bool,
     /// Earlier programs' endpoints it may call, in its next slots; each
     /// program's copy carries its own badge, so a server can tell them apart.
     pub uses: &'static [&'static str],
@@ -51,7 +57,8 @@ const fn server(name: &'static str, file: &'static [u8], limits: Limits) -> Prog
         file,
         limits,
         serves: true,
-        device: None,
+        devices: &[],
+        unlocks: false,
         uses: &[],
         storage: None,
         console: false,
@@ -63,16 +70,26 @@ const fn server(name: &'static str, file: &'static [u8], limits: Limits) -> Prog
 /// Started on every boot. The log server comes first so the rest can print.
 pub const SERVERS: &[Program] = &[
     Program { console: true, ..server("log", b"bin/log", SMALL) },
-    Program { device: Some(Device::Input), ..server("input", b"bin/input", Limits { regions: 4, ..SMALL }) },
+    Program { devices: &[Device::Input], ..server("input", b"bin/input", Limits { regions: 4, ..SMALL }) },
     // The input server's only client: it passes input on to the app in focus.
     Program {
-        device: Some(Device::Gpu),
+        devices: &[Device::Gpu],
         uses: &["input"],
         // The framebuffer alone is ~1000 pages at 1280x800.
         ..server("display", b"bin/display", Limits { pages: 1280, regions: 4, ..SMALL })
     },
     // Text on the display, lines from the keyboard (it takes input focus).
     Program { uses: &["display"], ..server("terminal", b"bin/terminal", SMALL) },
+    // Nothing that touches user data starts before the owner is in. It
+    // holds the screen (through the terminal), its keystore and randomness,
+    // and exits once it has handed over the key.
+    Program {
+        uses: &["terminal"],
+        devices: &[Device::Keystore, Device::Random],
+        unlocks: true,
+        // argon2's 16 MiB, its image and a little more.
+        ..server("gatekeeper", b"bin/gatekeeper", Limits { pages: 4096 + 160, regions: 6, ..SMALL })
+    },
     // The only one that equips apps (docs/apps.md): it reaches every app's
     // files and the owner's decisions, and runs apps through init.
     Program {
diff --git a/crates/kernel/src/tests/abi.rs b/crates/kernel/src/tests/abi.rs
index 2561ce4..b1fee40 100644
--- a/crates/kernel/src/tests/abi.rs
+++ b/crates/kernel/src/tests/abi.rs
@@ -70,7 +70,11 @@ fn out_of_range_arguments_do_not_decode() {
         decode(SYS_REQUEST_PAGES, &[0, 0, 0, 0, 0, 0]).is_none(),
         "zero pages"
     );
-    assert!(decode(SYS_REQUEST_PAGES, &[1025, 0, 0, 0, 0, 0]).is_none());
+    let too_many = types::bounded::PageCount::MAX as usize + 1;
+    assert!(
+        decode(SYS_REQUEST_PAGES, &[too_many, 0, 0, 0, 0, 0]).is_none(),
+        "more pages than one request may ask for"
+    );
     assert!(
         decode(SYS_MAP_REGION, &[1, 0x30000, 3, 0, 0, 0]).is_none(),
         "bad perms"
diff --git a/crates/libkos/src/alloc_impl.rs b/crates/libkos/src/alloc_impl.rs
index 1e43a5b..ca5c16e 100644
--- a/crates/libkos/src/alloc_impl.rs
+++ b/crates/libkos/src/alloc_impl.rs
@@ -3,7 +3,6 @@ use core::cell::UnsafeCell;
 use core::ptr;
 
 const PAGE_SIZE: usize = 4096;
-const MAX_PAGES: usize = 64;
 
 struct FreeBlock {
     size: usize,
@@ -14,10 +13,10 @@ pub struct KosAllocator {
     inner: UnsafeCell<AllocatorInner>,
 }
 
+/// How much heap a process gets is its page budget's business (the kernel
+/// enforces it), not the allocator's.
 struct AllocatorInner {
     free_list: *mut FreeBlock,
-    pages: [usize; MAX_PAGES],
-    page_count: usize,
 }
 
 unsafe impl Sync for KosAllocator {}
@@ -25,11 +24,7 @@ unsafe impl Sync for KosAllocator {}
 impl KosAllocator {
     pub const fn new() -> Self {
         Self {
-            inner: UnsafeCell::new(AllocatorInner {
-                free_list: ptr::null_mut(),
-                pages: [0; MAX_PAGES],
-                page_count: 0,
-            }),
+            inner: UnsafeCell::new(AllocatorInner { free_list: ptr::null_mut() }),
         }
     }
 
@@ -41,19 +36,12 @@ impl KosAllocator {
 impl AllocatorInner {
     /// `n` pages in one piece, so an allocation larger than a page fits.
     fn request_pages(&mut self, n: usize) -> *mut u8 {
-        if self.page_count + n > MAX_PAGES {
-            return ptr::null_mut();
-        }
         let Some(count) = u16::try_from(n).ok().and_then(types::bounded::PageCount::new) else {
             return ptr::null_mut();
         };
         let Some(va) = crate::syscall::request_pages(count) else {
             return ptr::null_mut();
         };
-        if let Some(slot) = self.pages.get_mut(self.page_count) {
-            *slot = va.raw();
-        }
-        self.page_count += n;
         va.raw() as *mut u8
     }
 
diff --git a/crates/libkos/src/terminal.rs b/crates/libkos/src/terminal.rs
index ff4cf62..36f4932 100644
--- a/crates/libkos/src/terminal.rs
+++ b/crates/libkos/src/terminal.rs
@@ -6,9 +6,18 @@ use types::bounded::CapSlot;
 
 /// Reads a typed line into `buf`, newline included if it fits; how much.
 pub fn read_line(terminal: CapSlot, buf: &mut [u8]) -> usize {
+    read(terminal, types::terminal::READ, buf)
+}
+
+/// Reads a typed line without showing it (`*` for each character).
+pub fn read_secret(terminal: CapSlot, buf: &mut [u8]) -> usize {
+    read(terminal, types::terminal::READ_SECRET, buf)
+}
+
+fn read(terminal: CapSlot, op: usize, buf: &mut [u8]) -> usize {
     let mut n = 0;
     while n < buf.len() {
-        let Ok(words) = syscall::request(terminal, [types::terminal::READ, 0, 0, 0]) else {
+        let Ok(words) = syscall::request(terminal, [op, 0, 0, 0]) else {
             break;
         };
         let Some((bytes, len)) = types::log::text_of(words) else {
diff --git a/crates/servers/gatekeeper/Cargo.toml b/crates/servers/gatekeeper/Cargo.toml
index 96e5c09..48c3242 100644
--- a/crates/servers/gatekeeper/Cargo.toml
+++ b/crates/servers/gatekeeper/Cargo.toml
@@ -6,3 +6,14 @@ edition = "2024"
 [dependencies]
 keystore = { workspace = true }
 zeroize = { workspace = true }
+types = { workspace = true }
+libkos = { workspace = true }
+port-block-device = { workspace = true }
+port-entropy = { workspace = true }
+driver-block-virtio = { workspace = true }
+driver-rng-virtio = { workspace = true }
+
+[[bin]]
+name = "gatekeeper"
+test = false
+bench = false
diff --git a/crates/servers/gatekeeper/src/devices.rs b/crates/servers/gatekeeper/src/devices.rs
new file mode 100644
index 0000000..89aeb1a
--- /dev/null
+++ b/crates/servers/gatekeeper/src/devices.rs
@@ -0,0 +1,55 @@
+//! The flow's ports on real devices: the keystore disk, virtio-rng, and
+//! the terminal.
+
+use libkos::io::print_to;
+use port_block_device::{BlockDevice, SectorId};
+use port_entropy::Entropy;
+use types::bounded::CapSlot;
+
+use crate::flow::{Keystore, MAX_SECRET, Prompt, Secret};
+use keystore::RECORD_SIZE;
+
+/// The record's two copies are its first two sectors.
+pub struct Disk<D: BlockDevice>(pub D);
+
+impl<D: BlockDevice> Keystore for Disk<D> {
+    fn read(&mut self, copy: usize, out: &mut [u8; RECORD_SIZE]) -> bool {
+        self.0.sector_size() == RECORD_SIZE && self.0.read_sector(SectorId::new(copy as u32), out)
+    }
+
+    fn write(&mut self, copy: usize, data: &[u8; RECORD_SIZE]) -> bool {
+        self.0.sector_size() == RECORD_SIZE && self.0.write_sector(SectorId::new(copy as u32), data)
+    }
+}
+
+pub struct Hardware<E: Entropy>(pub E);
+
+impl<E: Entropy> keystore::Random for Hardware<E> {
+    fn fill(&mut self, buf: &mut [u8]) -> bool {
+        self.0.fill(buf)
+    }
+}
+
+pub struct Terminal(pub CapSlot);
+
+impl Prompt for Terminal {
+    fn say(&mut self, text: &str) {
+        print_to(self.0, format_args!("{}", text));
+    }
+
+    fn clear(&mut self) {
+        libkos::terminal::clear(self.0);
+    }
+
+    fn secret(&mut self, question: &str, out: &mut Secret) -> bool {
+        print_to(self.0, format_args!("{}", question));
+        let mut line = Secret::new();
+        let mut buf = [0u8; MAX_SECRET + 1];
+        let n = libkos::terminal::read_secret(self.0, &mut buf);
+        let typed = buf[..n].strip_suffix(b"\n").unwrap_or(&buf[..n]);
+        line.set(typed);
+        buf.fill(0);
+        out.set(line.as_bytes());
+        n > 0
+    }
+}
diff --git a/crates/servers/gatekeeper/src/flow.rs b/crates/servers/gatekeeper/src/flow.rs
index 9a64454..87655ae 100644
--- a/crates/servers/gatekeeper/src/flow.rs
+++ b/crates/servers/gatekeeper/src/flow.rs
@@ -57,6 +57,8 @@ impl Drop for Secret {
 /// The owner, on the screen and keyboard.
 pub trait Prompt {
     fn say(&mut self, text: &str);
+    /// Blanks the screen.
+    fn clear(&mut self);
     /// Shows `question` and reads a passcode without showing it; false if
     /// nothing could be read.
     fn secret(&mut self, question: &str, out: &mut Secret) -> bool;
@@ -128,6 +130,8 @@ fn choose(prompt: &mut impl Prompt, question: &str, optional: bool, out: &mut Se
 /// A device never set up (or wiped): the owner chooses a passcode, and
 /// may choose a duress one. Returns the new master key.
 fn setup(ks: &mut impl Keystore, rng: &mut impl Random, prompt: &mut impl Prompt, params: KdfParams, memory: &mut [Block]) -> Result<Key, Failure> {
+    // After a wipe nothing earlier may show: it must look like a new device.
+    prompt.clear();
     prompt.say("This device has no passcode yet. Choose one; it protects everything on it.\n");
     let mut real = Secret::new();
     choose(prompt, "New passcode: ", false, &mut real)?;
diff --git a/crates/servers/gatekeeper/src/lib.rs b/crates/servers/gatekeeper/src/lib.rs
index c3074a5..a1bc2c9 100644
--- a/crates/servers/gatekeeper/src/lib.rs
+++ b/crates/servers/gatekeeper/src/lib.rs
@@ -7,8 +7,78 @@
 
 extern crate alloc;
 
+pub mod devices;
 pub mod flow;
 
 #[cfg(test)]
 #[path = "tests/mod.rs"]
 mod tests;
+
+use alloc::vec;
+use keystore::{Block, KdfParams};
+use libkos::syscall::{self, Received};
+use types::bounded::CapSlot;
+use types::gatekeeper::{KEY, UNLOCK, reply};
+
+/// Where init's manifest put them: its own endpoint (devices arrive on
+/// it, then init's calls), then the terminal.
+const EP: CapSlot = CapSlot::const_new(0);
+const TERMINAL: CapSlot = CapSlot::const_new(1);
+
+/// Answers init's next call, if it is `op`, with `words`.
+fn answer(op: usize, words: [usize; 4]) -> bool {
+    loop {
+        match syscall::receive_msg(EP) {
+            Ok(Received::Call { badge: 0, words: [w, ..], .. }) if w == op => {
+                return syscall::reply(words, None).is_ok();
+            }
+            // Anyone else, or anything else: refused.
+            Ok(Received::Call { .. }) => {
+                let _ = syscall::reply([reply::FAILED, 0, 0, 0], None);
+            }
+            Ok(_) => {}
+            Err(_) => return false,
+        }
+    }
+}
+
+pub fn run() -> ! {
+    // Init hands over the keystore disk, then the randomness device.
+    let keystore = libkos::device::receive_device(EP).mmio.and_then(driver_block_virtio::VirtioBlockDevice::new);
+    let random = libkos::device::receive_device(EP).mmio.and_then(driver_rng_virtio::VirtioRng::new);
+    let (Some(keystore), Some(random)) = (keystore, random) else {
+        libkos::println!("gatekeeper: no keystore or no randomness, nothing to unlock with");
+        let _ = answer(UNLOCK, [reply::FAILED, 0, 0, 0]);
+        syscall::exit();
+    };
+    let mut memory = vec![Block::default(); KdfParams::DEFAULT.memory_kib as usize];
+    libkos::println!("gatekeeper: waiting for the owner");
+    let key = flow::run(
+        &mut devices::Disk(keystore),
+        &mut devices::Hardware(random),
+        &mut devices::Terminal(TERMINAL),
+        KdfParams::DEFAULT,
+        &mut memory,
+    );
+    // The guesses' working memory goes before anything else happens.
+    for b in memory.iter_mut() {
+        *b = Block::default();
+    }
+    drop(memory);
+    match key {
+        Ok(key) => {
+            libkos::println!("gatekeeper: unlocked");
+            libkos::terminal::clear(TERMINAL);
+            let word = |i: usize| usize::from_le_bytes(key.0[i * 8..i * 8 + 8].try_into().unwrap_or([0; 8]));
+            if answer(UNLOCK, [reply::OK, 0, 0, 0]) {
+                let _ = answer(KEY, [word(0), word(1), word(2), word(3)]);
+            }
+        }
+        Err(why) => {
+            libkos::println!("gatekeeper: cannot go on: {:?}", why);
+            let _ = answer(UNLOCK, [reply::FAILED, 0, 0, 0]);
+        }
+    }
+    // Its capabilities go with it.
+    syscall::exit()
+}
diff --git a/crates/servers/gatekeeper/src/main.rs b/crates/servers/gatekeeper/src/main.rs
new file mode 100644
index 0000000..cfc000d
--- /dev/null
+++ b/crates/servers/gatekeeper/src/main.rs
@@ -0,0 +1,11 @@
+#![no_std]
+#![forbid(unsafe_code)]
+#![no_main]
+
+extern crate libkos;
+
+libkos::entry!(main);
+
+fn main() {
+    gatekeeper::run();
+}
diff --git a/crates/servers/gatekeeper/src/tests/mod.rs b/crates/servers/gatekeeper/src/tests/mod.rs
index 91579aa..2032dfe 100644
--- a/crates/servers/gatekeeper/src/tests/mod.rs
+++ b/crates/servers/gatekeeper/src/tests/mod.rs
@@ -67,18 +67,26 @@ impl Random for Counter {
 /// An owner typing from a script; what was shown is kept.
 struct Owner {
     typing: VecDeque<&'static str>,
+    /// On the screen now.
     shown: String,
+    /// Ever shown, cleared or not.
+    said: String,
 }
 
 impl Owner {
     fn types(lines: &[&'static str]) -> Self {
-        Self { typing: lines.iter().copied().collect(), shown: String::new() }
+        Self { typing: lines.iter().copied().collect(), shown: String::new(), said: String::new() }
     }
 }
 
 impl Prompt for Owner {
     fn say(&mut self, text: &str) {
         self.shown.push_str(text);
+        self.said.push_str(text);
+    }
+    /// What a fresh screen shows: nothing that came before.
+    fn clear(&mut self) {
+        self.shown.clear();
     }
     fn secret(&mut self, question: &str, out: &mut Secret) -> bool {
         self.shown.push_str(question);
@@ -158,7 +166,7 @@ fn too_many_wrong_passcodes_wipe_the_keys_and_the_device_starts_fresh() {
     guesses.extend(["5678", "5678", "", ""]);
     let mut owner = Owner::types(&guesses);
     let new = run_with(&mut dev, &mut owner).unwrap();
-    assert!(owner.shown.contains("One try left"));
+    assert!(owner.said.contains("One try left"));
     assert!(owner.shown.ends_with("This device has no passcode yet. Choose one; it protects everything on it.\nNew passcode: Again: A duress passcode wipes the device when it is entered instead. Leave it empty for none.\nDuress passcode: Again: "));
     assert_ne!(new.0, key, "the old master key is gone");
     let mut old = Owner::types(&["1234"]);
@@ -173,6 +181,7 @@ fn the_duress_passcode_wipes_silently_and_the_device_looks_fresh() {
     let mut owner = Owner::types(&["0000", "4321", "4321", "", ""]);
     let new = run_with(&mut dev, &mut owner).unwrap();
     assert!(!owner.shown.contains("Wrong"), "nothing tells it was a duress passcode");
+    assert!(owner.shown.starts_with("This device has no passcode yet"), "nor is the passcode prompt left showing");
     assert!(owner.shown.contains("no passcode yet"));
     assert_ne!(new.0, key);
 }
diff --git a/crates/servers/storage-server/src/protocol.rs b/crates/servers/storage-server/src/protocol.rs
index 10039b6..c0f790d 100644
--- a/crates/servers/storage-server/src/protocol.rs
+++ b/crates/servers/storage-server/src/protocol.rs
@@ -25,6 +25,8 @@ pub enum StorageRequest {
     Mkdir { path_len: usize },
     /// Carries the endpoint to print to.
     SetLog,
+    /// Half (`half`: 0 or 1) of the master key.
+    SetKey { half: usize, words: [usize; 2] },
     /// A capability to the path (`path_len` bytes of the buffer), inside
     /// the caller's scope.
     Grant {
@@ -74,6 +76,7 @@ impl Encode for StorageRequest {
             Delete { path_len } => [op::DELETE, path_len, 0, 0],
             Mkdir { path_len } => [op::MKDIR, path_len, 0, 0],
             SetLog => [op::SET_LOG, 0, 0, 0],
+            SetKey { half, words } => [op::SET_KEY, half, words[0], words[1]],
             Grant { path_len, write } => [op::GRANT, path_len, usize::from(write), 0],
             Release => [op::RELEASE, 0, 0, 0],
         }
@@ -95,6 +98,7 @@ impl Decode for StorageRequest {
             op::DELETE => Delete { path_len: w[1] },
             op::MKDIR => Mkdir { path_len: w[1] },
             op::SET_LOG => SetLog,
+            op::SET_KEY => SetKey { half: w[1], words: [w[2], w[3]] },
             op::GRANT => Grant {
                 path_len: w[1],
                 write: w[2] != 0,
diff --git a/crates/servers/storage-server/src/server.rs b/crates/servers/storage-server/src/server.rs
index ca0ff20..d081533 100644
--- a/crates/servers/storage-server/src/server.rs
+++ b/crates/servers/storage-server/src/server.rs
@@ -50,6 +50,9 @@ pub struct StorageServer<F: FileSystem, H: Host> {
     clients: [Option<Client>; MAX_CLIENTS],
     owners: [Option<Owner>; MAX_HANDLES],
     log: Option<CapSlot>,
+    /// The master key's halves, from the gatekeeper through init: what the
+    /// disk's encryption will be keyed with.
+    key: [Option<[usize; 2]>; 2],
 }
 
 impl<F: FileSystem, H: Host> StorageServer<F, H> {
@@ -61,6 +64,7 @@ impl<F: FileSystem, H: Host> StorageServer<F, H> {
             clients: [const { None }; MAX_CLIENTS],
             owners: [None; MAX_HANDLES],
             log: None,
+            key: [None; 2],
         }
     }
 
@@ -83,6 +87,23 @@ impl<F: FileSystem, H: Host> StorageServer<F, H> {
         }
     }
 
+    /// Only the unbadged holder (init), each half only once: nobody can
+    /// replace the key later.
+    fn set_key(&mut self, badge: usize, half: usize, words: [usize; 2]) -> StorageResponse {
+        match (badge, self.key.get_mut(half)) {
+            (0, Some(slot @ None)) => {
+                *slot = Some(words);
+                StorageResponse::Ok
+            }
+            _ => StorageResponse::Error,
+        }
+    }
+
+    /// Whether the whole master key has arrived.
+    pub fn unlocked(&self) -> bool {
+        self.key.iter().all(Option::is_some)
+    }
+
     pub fn filesystem(&self) -> &F {
         &self.fs
     }
@@ -265,7 +286,7 @@ impl<F: FileSystem, H: Host> StorageServer<F, H> {
             None => R::NotFound,
         };
         let response = match request {
-            Attach | SetLog | Release => R::Error,
+            Attach | SetLog | SetKey { .. } | Release => R::Error,
             Grant { path_len, write } => {
                 let narrower = scope.narrow(&buf[sent(path_len)], write);
                 return match narrower.and_then(|s| grants.add(badge, s, |b| host.mint(b))) {
@@ -368,6 +389,7 @@ impl<F: FileSystem, H: Host> Server for StorageServer<F, H> {
     ) -> ([usize; 4], Option<Give>) {
         match StorageRequest::decode(words) {
             Some(StorageRequest::SetLog) => (self.set_log(badge, cap).encode(), None),
+            Some(StorageRequest::SetKey { half, words }) => (self.set_key(badge, half, words).encode(), None),
             // A badge storage never issued, or one it has taken back.
             Some(request) => match self.grants.scope(badge) {
                 None => (StorageResponse::Denied.encode(), None),
diff --git a/crates/servers/storage-server/src/tests/protocol.rs b/crates/servers/storage-server/src/tests/protocol.rs
index 209db2c..3c08618 100644
--- a/crates/servers/storage-server/src/tests/protocol.rs
+++ b/crates/servers/storage-server/src/tests/protocol.rs
@@ -25,6 +25,7 @@ fn every_request_roundtrips() {
             write: false,
         },
         StorageRequest::Release,
+        StorageRequest::SetKey { half: 1, words: [7, 9] },
     ] {
         assert_eq!(StorageRequest::decode(req.encode()), Some(req));
     }
diff --git a/crates/servers/storage-server/src/tests/server.rs b/crates/servers/storage-server/src/tests/server.rs
index 3c1cc7d..ea436c5 100644
--- a/crates/servers/storage-server/src/tests/server.rs
+++ b/crates/servers/storage-server/src/tests/server.rs
@@ -472,3 +472,16 @@ fn the_unbadged_holder_cannot_be_released() {
         StorageResponse::Error
     );
 }
+
+#[test]
+fn only_init_sets_the_key_and_only_once() {
+    let mut s = server();
+    let set = |s: &mut Srv, badge, half| call(s, badge, StorageRequest::SetKey { half, words: [1, 2] }).0;
+    assert_eq!(set(&mut s, 5, 0), StorageResponse::Error, "a client cannot");
+    assert_eq!(set(&mut s, 0, 0), StorageResponse::Ok);
+    assert!(!s.unlocked());
+    assert_eq!(set(&mut s, 0, 0), StorageResponse::Error, "nor can it be replaced");
+    assert_eq!(set(&mut s, 0, 2), StorageResponse::Error, "two halves only");
+    assert_eq!(set(&mut s, 0, 1), StorageResponse::Ok);
+    assert!(s.unlocked());
+}
diff --git a/crates/servers/terminal-server/src/server.rs b/crates/servers/terminal-server/src/server.rs
index 3f778af..cbca61b 100644
--- a/crates/servers/terminal-server/src/server.rs
+++ b/crates/servers/terminal-server/src/server.rs
@@ -157,9 +157,9 @@ impl<C: Console> TerminalServer<C> {
         }
     }
 
-    /// Edits a line from the keyboard, echoing it, until Enter. Ctrl+C
-    /// drops it and reads as an empty line.
-    fn read_line(&mut self) {
+    /// Edits a line from the keyboard, echoing it (as `*` if `secret`),
+    /// until Enter. Ctrl+C drops it and reads as an empty line.
+    fn read_line(&mut self, secret: bool) {
         self.console.flush();
         // Flushed now; a flush timer still running is harmless.
         self.flush_pending = false;
@@ -190,7 +190,7 @@ impl<C: Console> TerminalServer<C> {
                 b if self.line_len + 1 < MAX_LINE && (b' '..=b'~').contains(&b) => {
                     self.line[self.line_len] = b;
                     self.line_len += 1;
-                    self.grid.put(b);
+                    self.grid.put(if secret { b'*' } else { b });
                 }
                 _ => continue,
             }
@@ -202,14 +202,18 @@ impl<C: Console> TerminalServer<C> {
     }
 
     /// The next chunk of the typed line, reading one first if none is left.
-    fn read(&mut self) -> [usize; 4] {
+    /// A secret line never reaches the screen, and is forgotten once read.
+    fn read(&mut self, secret: bool) -> [usize; 4] {
         if self.line_read == self.line_len {
-            self.read_line();
+            self.read_line(secret);
         }
         let end = (self.line_read + TEXT_BYTES).min(self.line_len);
-        let chunk = &self.line[self.line_read..end];
+        let words = text_words(&self.line[self.line_read..end]);
         self.line_read = end;
-        text_words(chunk)
+        if secret && self.line_read == self.line_len {
+            self.line.fill(0);
+        }
+        words
     }
 }
 
@@ -230,7 +234,8 @@ impl<C: Console> Server for TerminalServer<C> {
 
     fn handle_call(&mut self, _badge: usize, words: [usize; 4], cap: Option<CapSlot>) -> ([usize; 4], Option<libkos::syscall::Give>) {
         let reply = match words[0] {
-            types::terminal::READ => self.read(),
+            types::terminal::READ => self.read(false),
+            types::terminal::READ_SECRET => self.read(true),
             types::terminal::REDRAW => {
                 // Taking focus back clears the screen.
                 self.console.take_focus();
diff --git a/crates/servers/terminal-server/src/tests/server.rs b/crates/servers/terminal-server/src/tests/server.rs
index b371048..78c3456 100644
--- a/crates/servers/terminal-server/src/tests/server.rs
+++ b/crates/servers/terminal-server/src/tests/server.rs
@@ -176,3 +176,13 @@ fn rows_are_drawn_only_as_wide_as_their_text_or_what_it_replaces() {
     // Cleared: the old five cells and the cursor after them are erased.
     assert!(t.console().rows_drawn.contains(&(0, 6)), "{:?}", t.console().rows_drawn);
 }
+
+#[test]
+fn a_secret_line_shows_stars_and_is_forgotten() {
+    let mut t = term(b"hunter2\n");
+    let (words, _) = t.handle_call(1, [types::terminal::READ_SECRET, 0, 0, 0], None);
+    let (bytes, len) = text_of(words).unwrap();
+    assert_eq!(&bytes[..len], b"hunter2\n");
+    assert_eq!(&t.grid().row(0)[..8], b"*******\x20");
+    assert!(!t.grid().row(0).windows(7).any(|w| w == b"hunter2"));
+}
diff --git a/crates/types/src/bounded.rs b/crates/types/src/bounded.rs
index 2213391..dfde17a 100644
--- a/crates/types/src/bounded.rs
+++ b/crates/types/src/bounded.rs
@@ -3,7 +3,9 @@ use crate::macros::bounded;
 // Kani runs the real kernel with tiny tables; see kernel/src/proofs.
 bounded!(CapSlot, u8, 0, if cfg!(kani) { 3 } else { 63 });
 bounded!(Priority, u8, 0, 31);
-bounded!(PageCount, u16, 1, 1024);
+// Up to a process's whole address window (32 MiB): one request may be big (a
+// KDF's memory); budgets bound how much anyone gets.
+bounded!(PageCount, u16, 1, 8192);
 
 impl Priority {
     pub const DEFAULT: Self = Self(16);
diff --git a/crates/types/src/gatekeeper.rs b/crates/types/src/gatekeeper.rs
new file mode 100644
index 0000000..7430140
--- /dev/null
+++ b/crates/types/src/gatekeeper.rs
@@ -0,0 +1,13 @@
+//! Init and the gatekeeper: after handing it the keystore and randomness
+//! (device setup calls), init calls `UNLOCK`, which returns once the owner
+//! is authenticated (`OK`) or the gatekeeper cannot go on (`FAILED`); then
+//! `KEY`, whose reply is the 32-byte master key in its four words. The
+//! gatekeeper then exits. Only the unbadged holder (init) is answered.
+
+pub const UNLOCK: usize = 1;
+pub const KEY: usize = 2;
+
+pub mod reply {
+    pub const OK: usize = 0;
+    pub const FAILED: usize = 1;
+}
diff --git a/crates/types/src/lib.rs b/crates/types/src/lib.rs
index 5ee6b8e..6859c39 100644
--- a/crates/types/src/lib.rs
+++ b/crates/types/src/lib.rs
@@ -8,6 +8,7 @@ pub mod bootinfo;
 pub mod bounded;
 pub mod budget;
 pub mod display;
+pub mod gatekeeper;
 pub mod generation;
 pub mod id;
 pub mod input;
diff --git a/crates/types/src/storage.rs b/crates/types/src/storage.rs
index e2b0a0b..6875d15 100644
--- a/crates/types/src/storage.rs
+++ b/crates/types/src/storage.rs
@@ -33,6 +33,9 @@ pub mod op {
     /// Takes back the grant this is called through, and everything
     /// granted from it, from every holder.
     pub const RELEASE: usize = 12;
+    /// Half the master key (word 1: which half, words 2..4: it), from the
+    /// unbadged holder (init) only, each half once.
+    pub const SET_KEY: usize = 13;
 }
 
 /// Reply tags (word 0).
diff --git a/crates/types/src/terminal.rs b/crates/types/src/terminal.rs
index 31c5faa..aa10ad7 100644
--- a/crates/types/src/terminal.rs
+++ b/crates/types/src/terminal.rs
@@ -5,6 +5,9 @@
 /// the line's last chunk ends with `\n`. Blocks until a line is entered.
 pub const READ: usize = 10;
 pub const CLEAR: usize = 11;
+/// As `READ`, but what is typed shows as `*` and is forgotten once read:
+/// for passcodes.
+pub const READ_SECRET: usize = 14;
 /// Repaints the whole screen and takes input focus back, after a program
 /// that drew on the screen itself.
 pub const REDRAW: usize = 12;
diff --git a/docs/ipc.md b/docs/ipc.md
index 1603641..84da8d3 100644
--- a/docs/ipc.md
+++ b/docs/ipc.md
@@ -91,6 +91,17 @@ and budget listed there. Storage, started before the log server, receives
 its log endpoint from init later (`SET_LOG`, accepted only from the
 unbadged holder of its endpoint).
 
+Nothing that touches user data starts before the owner is authenticated.
+Init starts the log, input, display and terminal servers, then the
+gatekeeper (`types::gatekeeper`), handing it only the terminal, the keystore
+(a small disk of its own, told from the data disk by its size) and the
+virtio-rng device. Init calls `UNLOCK`, which returns once the owner is in,
+then `KEY`, whose reply is the master key; init passes it to storage
+(`SET_KEY`, from the unbadged holder only, each half once) and only then
+starts the permission manager and the desktop. If the gatekeeper cannot
+unlock, init stops there. The gatekeeper exits, and its capabilities go
+with it.
+
 A program's `uses` endpoints arrive as badged copies with `Execute` and
 `Delegate`: the badge (unique per copy) tells the server which client is
 calling, and `Delegate` lets the client send capabilities with its calls
diff --git a/scripts/make-disk-image.sh b/scripts/make-disk-image.sh
index bda5975..fcc9c59 100755
--- a/scripts/make-disk-image.sh
+++ b/scripts/make-disk-image.sh
@@ -46,6 +46,7 @@ copy permission-manager permission
 copy session-server     session
 copy terminal-server    terminal
 copy shell              shell
+copy gatekeeper         gatekeeper
 # Apps.
 app cat
 app ls
diff --git a/scripts/test-qemu.sh b/scripts/test-qemu.sh
index bb20b06..9312868 100755
--- a/scripts/test-qemu.sh
+++ b/scripts/test-qemu.sh
@@ -1,20 +1,58 @@
 #!/bin/bash
 # Boots IMAGE headless and waits for the self-test (init's SMP checks, then
-# spawntest) to report; the machine halts itself when done. Exit 0 only on
-# "SMPTEST PASS".
+# spawntest) to report; the machine halts itself when done. Twice, on one
+# fresh keystore: the first boot sets a passcode up at the gatekeeper, the
+# second gets it wrong once and then right. Exit 0 only if both unlock and
+# both say "SMPTEST PASS".
 set -uo pipefail
 
 IMAGE="${1:?usage: test-qemu.sh IMAGE}"
 SMP="${SMP:-4}"
 KERNEL="target/riscv64gc-unknown-none-elf/release/adapter-riscv"
 LOG="$(mktemp -t kos-test-qemu.XXXXXX)"
+KEYS="${LOG}.keys"
+MON="${LOG}.mon"
+truncate -s 64K "${KEYS}"
 
-timeout ${QT:-120} qemu-system-riscv64 -machine virt -smp "${SMP}" -bios default \
-    -kernel "${KERNEL}" \
-    -drive "file=${IMAGE},if=none,format=raw,id=hd0" -device virtio-blk-device,drive=hd0 \
-    -device virtio-gpu-device -device virtio-keyboard-device \
-    -display none -serial "file:${LOG}" -monitor none
+# Types `lines` (one per argument) at the gatekeeper once it waits.
+owner() {
+    for _ in $(seq 300); do grep -aq "gatekeeper: waiting" "${LOG}" 2>/dev/null && break; sleep 0.2; done
+    for line in "$@"; do
+        for ((i = 0; i < ${#line}; i++)); do
+            echo "sendkey ${line:i:1}" | socat - "unix-connect:${MON}" >/dev/null 2>&1; sleep 0.05
+        done
+        echo "sendkey ret" | socat - "unix-connect:${MON}" >/dev/null 2>&1; sleep 0.3
+    done
+}
+
+# One boot; `owner` types the arguments. Its serial output lands in LOG.
+boot() {
+    : > "${LOG}"; rm -f "${MON}"
+    owner "$@" &
+    timeout ${QT:-120} qemu-system-riscv64 -machine virt -smp "${SMP}" -bios default \
+        -kernel "${KERNEL}" \
+        -drive "file=${IMAGE},if=none,format=raw,id=hd0" -device virtio-blk-device,drive=hd0 \
+        -drive "file=${KEYS},if=none,format=raw,id=ks" -device virtio-blk-device,drive=ks \
+        -device virtio-rng-device -device virtio-gpu-device -device virtio-keyboard-device \
+        -display none -serial "file:${LOG}" -monitor "unix:${MON},server,nowait"
+    local s=$?
+    wait
+    return $s
+}
+
+# First boot: a new passcode (twice), no duress passcode (twice empty).
+boot 1234 1234 "" ""
 status=$?
+first_ok=0
+grep -aq "the owner is in" "${LOG}" && grep -aq "SMPTEST PASS" "${LOG}" && first_ok=1
+echo "test-qemu: first boot: passcode set up: $([ ${first_ok} -eq 1 ] && echo ok || echo FAIL)"
+# Second boot: the keystore remembers; a wrong guess, then the passcode.
+boot 9999 1234
+[ ${status} -eq 0 ] && status=$?
+second_ok=0
+grep -aq "the owner is in" "${LOG}" && second_ok=1
+echo "test-qemu: second boot: wrong passcode refused, right one unlocks: $([ ${second_ok} -eq 1 ] && echo ok || echo FAIL)"
+rm -f "${KEYS}" "${MON}"
 
 grep -a "smptest:\|spawntest:\|Hello\|SMPTEST" "${LOG}"
 # What k-os wrote must be ext4 that the real tools accept.
@@ -29,7 +67,7 @@ if command -v e2fsck >/dev/null && command -v debugfs >/dev/null; then
     fi
     rm -f "${LOG}.fsck"
 fi
-if [ "${disk_ok}" -eq 1 ] && grep -aq "SMPTEST PASS" "${LOG}"; then
+if [ "${disk_ok}" -eq 1 ] && [ ${first_ok} -eq 1 ] && [ ${second_ok} -eq 1 ] && grep -aq "SMPTEST PASS" "${LOG}"; then
     echo "test-qemu: pass (${SMP} harts)"
     rm -f "${LOG}"
     exit 0