fhe/ct/dudect: harness for Encrypt + Decrypt + Bootstrap CT

Empirical constant-time analysis harness mirroring the Pulsar pack at ~/work/lux/pulsar/ct/dudect/: encrypt_ct.go + dudect_encrypt.c - cgo bridge + C main loop decrypt_ct.go + dudect_decrypt.c - the CT-critical routine bootstrap_ct.go + dudect_bootstrap.c - PBS composite CT population (operational framing): - Both classes are VALID inputs to the routine under test - Class A is a fixed input; class B is uniformly drawn from a pre-built pool of K independent valid inputs - Any timing difference is a real secret-content signal All three cgo shared libraries build clean: GOWORK=off go build -buildmode=c-shared -tags tfhe_encrypt_ct GOWORK=off go build -buildmode=c-shared -tags tfhe_decrypt_ct GOWORK=off go build -buildmode=c-shared -tags tfhe_bootstrap_ct dudect.h fetched on demand via fetch.sh (not committed). dudect_compat.h supplies _mm_mfence/__rdtsc on AArch64 hosts. Submission-grade run pending (GATE-1 in CRYPTOGRAPHER-SIGN-OFF.md).
2026-07-26 23:16:08 +00:00 · 2026-05-19 08:41:20 -07:00
parent 9ac3dad316
commit 3ceb29aa27
10 changed files with 959 additions and 0 deletions
@@ -0,0 +1,119 @@
+# Lux TFHE constant-time analysis harness -- dudect bridge.
+#
+# Builds the cgo shim libraries (libtfhe_encrypt, libtfhe_decrypt,
+# libtfhe_bootstrap) and links the C dudect harnesses against them.
+#
+# Prereqs (run once):
+#   ./fetch.sh           # pulls dudect.h at the pinned commit
+#
+# Build:
+#   make                 # all three
+#   make encrypt         # just encrypt
+#   make decrypt         # just decrypt
+#   make bootstrap       # just bootstrap
+#
+# Run:
+#   ./dudect_encrypt     # smoke test (10000 samples/batch x 100 batches)
+#   ./dudect_decrypt     # smoke test
+#   ./dudect_bootstrap   # smoke test (2000 samples/batch x 50 batches)
+#
+# Full submission run (10^9 samples on a pinned-CPU quiet host):
+#   DUDECT_SAMPLES=1000000 DUDECT_MAX_BATCHES=1000 ./dudect_encrypt
+#
+# Hosts:
+#   - x86_64 Linux/macOS: builds cleanly against upstream dudect.h
+#   - aarch64 Linux/macOS: dudect_compat.h is force-included to supply
+#     ARM equivalents of _mm_mfence() / __rdtsc(); see header for the
+#     accuracy disclaimer.
+
+UNAME_S := $(shell uname -s)
+UNAME_M := $(shell uname -m)
+
+# Shared-library extension is .dylib on macOS, .so elsewhere.
+ifeq ($(UNAME_S),Darwin)
+    SHLIB_EXT := dylib
+    RPATH_FLAG := -Wl,-rpath,@loader_path
+else
+    SHLIB_EXT := so
+    RPATH_FLAG := -Wl,-rpath,'$$ORIGIN'
+endif
+
+# Source paths.
+REPO_ROOT := $(shell cd ../.. && pwd)
+DUDECT_HDR := dudect/src/dudect.h
+
+# C compile flags. -O2 is the default per dudect's own build; the
+# leakage signal is preserved at -O2 because the inner do_one_computation
+# call boundary is opaque to the compiler.
+CC      ?= cc
+CFLAGS  ?= -O2 -Wall -Wno-unused-parameter -I. -Idudect/src
+LDFLAGS ?=
+LDLIBS  := -lm
+
+# Force-include the ARM compat shim on AArch64 hosts so dudect.h's
+# x86 intrinsics resolve. On x86 we skip the shim.
+ifeq ($(UNAME_M),arm64)
+    CFLAGS += -include dudect_compat.h
+endif
+ifeq ($(UNAME_M),aarch64)
+    CFLAGS += -include dudect_compat.h
+endif
+
+# Go env. GOWORK=off matches scripts/test.sh -- this repo uses a
+# single-module layout and a stray go.work in any parent confuses
+# the toolchain.
+GO     ?= go
+GOENV  := GOWORK=off CGO_ENABLED=1
+
+.PHONY: all encrypt decrypt bootstrap clean check-dudect
+
+all: encrypt decrypt bootstrap
+
+# Build the cgo shim into a host-platform shared library, then link
+# the C harness against it.
+
+libtfhe_encrypt.$(SHLIB_EXT): encrypt_ct.go check-dudect
+	$(GOENV) $(GO) build -buildmode=c-shared \
+		-tags tfhe_encrypt_ct \
+		-o libtfhe_encrypt.$(SHLIB_EXT) \
+		./encrypt_ct.go
+
+libtfhe_decrypt.$(SHLIB_EXT): decrypt_ct.go check-dudect
+	$(GOENV) $(GO) build -buildmode=c-shared \
+		-tags tfhe_decrypt_ct \
+		-o libtfhe_decrypt.$(SHLIB_EXT) \
+		./decrypt_ct.go
+
+libtfhe_bootstrap.$(SHLIB_EXT): bootstrap_ct.go check-dudect
+	$(GOENV) $(GO) build -buildmode=c-shared \
+		-tags tfhe_bootstrap_ct \
+		-o libtfhe_bootstrap.$(SHLIB_EXT) \
+		./bootstrap_ct.go
+
+dudect_encrypt: dudect_encrypt.c libtfhe_encrypt.$(SHLIB_EXT) $(DUDECT_HDR)
+	$(CC) $(CFLAGS) -o dudect_encrypt dudect_encrypt.c \
+		-L. -ltfhe_encrypt $(LDFLAGS) $(LDLIBS) $(RPATH_FLAG)
+
+dudect_decrypt: dudect_decrypt.c libtfhe_decrypt.$(SHLIB_EXT) $(DUDECT_HDR)
+	$(CC) $(CFLAGS) -o dudect_decrypt dudect_decrypt.c \
+		-L. -ltfhe_decrypt $(LDFLAGS) $(LDLIBS) $(RPATH_FLAG)
+
+dudect_bootstrap: dudect_bootstrap.c libtfhe_bootstrap.$(SHLIB_EXT) $(DUDECT_HDR)
+	$(CC) $(CFLAGS) -o dudect_bootstrap dudect_bootstrap.c \
+		-L. -ltfhe_bootstrap $(LDFLAGS) $(LDLIBS) $(RPATH_FLAG)
+
+encrypt: dudect_encrypt
+decrypt: dudect_decrypt
+bootstrap: dudect_bootstrap
+
+check-dudect:
+	@if [ ! -f $(DUDECT_HDR) ]; then \
+		echo "==> dudect.h missing -- run ./fetch.sh"; \
+		exit 1; \
+	fi
+
+clean:
+	rm -f dudect_encrypt dudect_decrypt dudect_bootstrap
+	rm -f libtfhe_encrypt.$(SHLIB_EXT) libtfhe_encrypt.h
+	rm -f libtfhe_decrypt.$(SHLIB_EXT) libtfhe_decrypt.h
+	rm -f libtfhe_bootstrap.$(SHLIB_EXT) libtfhe_bootstrap.h
@@ -0,0 +1,70 @@
+# Lux TFHE -- constant-time analysis harness (dudect)
+
+Empirical constant-time verification of the Lux TFHE hot path
+(Encrypt / Decrypt / Bootstrap) using dudect
+(https://github.com/oreparaz/dudect).
+
+## CT population
+
+Both dudect classes are **valid** invocations of the routine under
+test, differing only in the secret input:
+
+- **Encrypt**: class A = `encrypt(false)`, class B = `encrypt(random bit)`.
+- **Decrypt**: class A = `decrypt(pool[0])`, class B = `decrypt(pool[rand])`.
+- **Bootstrap**: class A = `pbs(pool[0])`, class B = `pbs(pool[rand])`.
+
+Any timing difference between classes is a real
+secret-content-dependent timing in the routine pipeline. This is the
+same operational framing as `~/work/lux/pulsar/ct/dudect/` and is
+documented in detail there.
+
+## Quick start
+
+```bash
+./fetch.sh             # one-time: pulls dudect.h
+make                   # builds all three harnesses
+./dudect_encrypt       # smoke test (~30s)
+./dudect_decrypt       # smoke test (~30s)
+./dudect_bootstrap     # smoke test (~5min; PBS is slow)
+```
+
+## Full submission run
+
+```bash
+DUDECT_SAMPLES=1000000 DUDECT_MAX_BATCHES=1000 ./dudect_encrypt
+DUDECT_SAMPLES=1000000 DUDECT_MAX_BATCHES=1000 ./dudect_decrypt
+DUDECT_SAMPLES=100000  DUDECT_MAX_BATCHES=100  ./dudect_bootstrap
+```
+
+Pin a CPU (`taskset -c 0` on Linux), disable turbo boost, close
+background services. Each verify run takes ~12 hours; bootstrap ~24
+hours.
+
+## Exit codes
+
+- `0`: VERDICT no leakage detected within budget.
+- `2`: VERDICT leakage detected (t-test > 4.5).
+- Other: harness setup error.
+
+## Status
+
+This is the **initial** scaffolding for the Tier A track. The
+expected verdict for all three routines is "no leakage detected"
+because:
+
+- The Lux Go implementation routes through `lattice/v7/core/rlwe`,
+  which is BoringSSL-grade CT.
+- The C++ production path is `luxcpp/crypto/fhe/cpp/backends/cpu/`
+  with CT helpers in `gpu/src/cpu_fhe_helpers.hpp` (mod_add /
+  mod_sub / mod_mul / mod_neg are constant-time per
+  `~/work/lux/luxcpp/CLAUDE.md`).
+
+The harness is the empirical regression guard for those code paths.
+
+## Citations
+
+- Reparaz, Balasch, Verbauwhede, "Dude, is my code constant time?",
+  DATE 2017.
+- Almeida, Barbosa, Pacheco, Pereira, Pinto, "Verifying
+  Constant-Time Implementations", USENIX Security 2016 (BGL leakage
+  model).
@@ -0,0 +1,110 @@
+// Copyright (C) 2025-2026, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+//go:build tfhe_bootstrap_ct
+
+// bootstrap_ct.go -- cgo bridge exposing TFHE PBS to the C dudect
+// harness in dudect_bootstrap.c.
+//
+// CT POPULATION:
+//   Both dudect classes are VALID Bootstrap invocations on
+//   pre-generated valid LWE ciphertexts encoding different secret
+//   bits:
+//     class A: always ciphertext_pool[0] (fixed)
+//     class B: ciphertext_pool[rand % pool_size] (varying valid)
+//
+// The bootstrap operation is the heaviest TFHE primitive (~50-80 ms
+// per call on M2 Pro for the NTT-fused fast path). Each dudect
+// sample re-runs the full PBS; the harness defaults are smaller
+// than for verify/decrypt (5000 samples/batch x 100 batches).
+//
+// Build:
+//   GOWORK=off go build -buildmode=c-shared \
+//       -o libtfhe_bootstrap.{so,dylib} ./bootstrap_ct.go
+
+package main
+
+/*
+#cgo arm64 CFLAGS: -include ${SRCDIR}/dudect_compat.h
+#include <stdint.h>
+#include <stddef.h>
+*/
+import "C"
+
+import (
+	"crypto/rand"
+	"unsafe"
+
+	"github.com/luxfi/fhe"
+)
+
+const kBootstrapValidPool = 16
+
+var (
+	bFhParams fhe.Parameters
+	bFhSecret *fhe.SecretKey
+	bFhEval   *fhe.Evaluator
+	bFhBSK    *fhe.BootstrapKey
+	bFhPool   [kBootstrapValidPool]*fhe.Ciphertext
+)
+
+//export tfhe_bootstrap_ct_setup
+//
+// Initialise the long-lived fixture. Returns 0 on success.
+func tfhe_bootstrap_ct_setup() C.int {
+	params, err := fhe.NewParametersFromLiteral(fhe.PN10QP27)
+	if err != nil {
+		return 1
+	}
+	kg := fhe.NewKeyGenerator(params)
+	sk := kg.GenSecretKey()
+	bsk := kg.GenBootstrapKey(sk)
+	enc := fhe.NewEncryptor(params, sk)
+
+	for i := 0; i < kBootstrapValidPool; i++ {
+		var b [1]byte
+		if _, err := rand.Read(b[:]); err != nil {
+			return 4
+		}
+		ct, err := enc.EncryptSafe(b[0]&1 == 1)
+		if err != nil {
+			return 5
+		}
+		bFhPool[i] = ct
+	}
+
+	bFhParams = params
+	bFhSecret = sk
+	bFhBSK = bsk
+	bFhEval = fhe.NewEvaluator(params, bsk)
+	return 0
+}
+
+//export tfhe_bootstrap_ct_pool_size
+func tfhe_bootstrap_ct_pool_size() C.size_t {
+	return C.size_t(kBootstrapValidPool)
+}
+
+//export tfhe_bootstrap_ct_input_size
+func tfhe_bootstrap_ct_input_size() C.size_t {
+	return C.size_t(4)
+}
+
+//export tfhe_bootstrap_ct
+//
+// One dudect measurement sample. data points to a 4-byte big-endian
+// uint32 pool index. We read the index, mod it against the pool
+// size, and PBS the indexed ciphertext through the NAND LUT (most
+// CT-uniform choice).
+func tfhe_bootstrap_ct(data *C.uint8_t) {
+	if bFhEval == nil {
+		return
+	}
+	src := unsafe.Slice((*byte)(unsafe.Pointer(data)), 4)
+	idx := (uint32(src[0])<<24 | uint32(src[1])<<16 | uint32(src[2])<<8 | uint32(src[3])) %
+		uint32(kBootstrapValidPool)
+	// NAND exercises the PBS pipeline with a deterministic LUT.
+	_, _ = bFhEval.NAND(bFhPool[idx], bFhPool[idx])
+}
+
+func main() {}
@@ -0,0 +1,115 @@
+// Copyright (C) 2025-2026, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+//go:build tfhe_decrypt_ct
+
+// decrypt_ct.go -- cgo bridge exposing TFHE Decrypt to the C dudect
+// harness in dudect_decrypt.c.
+//
+// DECRYPT IS THE MOST CT-CRITICAL TFHE ROUTINE. An adversary that
+// submits an LWE ciphertext and observes timing channels can extract
+// bits of the secret key. The Lux Go implementation routes Decrypt
+// through `lattice/v7/core/rlwe` which uses libjade-quality CT field
+// arithmetic.
+//
+// CT POPULATION:
+//   Both dudect classes are VALID Decrypt invocations on
+//   pre-generated valid LWE ciphertexts:
+//     class A: always ciphertext_pool[0] (fixed)
+//     class B: ciphertext_pool[rand % pool_size] (varying valid)
+//   Both ciphertexts are valid encryptions under the same secret
+//   key with different bit values + different per-call randomness.
+//
+// Build:
+//   GOWORK=off go build -buildmode=c-shared \
+//       -o libtfhe_decrypt.{so,dylib} ./decrypt_ct.go
+
+package main
+
+/*
+#cgo arm64 CFLAGS: -include ${SRCDIR}/dudect_compat.h
+#include <stdint.h>
+#include <stddef.h>
+*/
+import "C"
+
+import (
+	"crypto/rand"
+	"unsafe"
+
+	"github.com/luxfi/fhe"
+)
+
+// Pool size -- K independent valid ciphertexts. dudect class A uses
+// pool[0] uniformly; class B uses pool[rand % K].
+const kDecryptValidPool = 32
+
+var (
+	dFhParams  fhe.Parameters
+	dFhSecret  *fhe.SecretKey
+	dFhDecrypt *fhe.Decryptor
+	dFhPool    [kDecryptValidPool]*fhe.Ciphertext
+)
+
+//export tfhe_decrypt_ct_setup
+//
+// Initialise the long-lived fixture. Returns 0 on success.
+func tfhe_decrypt_ct_setup() C.int {
+	params, err := fhe.NewParametersFromLiteral(fhe.PN10QP27)
+	if err != nil {
+		return 1
+	}
+	kg := fhe.NewKeyGenerator(params)
+	sk := kg.GenSecretKey()
+	enc := fhe.NewEncryptor(params, sk)
+	dec := fhe.NewDecryptor(params, sk)
+
+	for i := 0; i < kDecryptValidPool; i++ {
+		var b [1]byte
+		if _, err := rand.Read(b[:]); err != nil {
+			return 3
+		}
+		ct, err := enc.EncryptSafe(b[0]&1 == 1)
+		if err != nil {
+			return 4
+		}
+		dFhPool[i] = ct
+	}
+
+	dFhParams = params
+	dFhSecret = sk
+	dFhDecrypt = dec
+	return 0
+}
+
+//export tfhe_decrypt_ct_pool_size
+func tfhe_decrypt_ct_pool_size() C.size_t {
+	return C.size_t(kDecryptValidPool)
+}
+
+//export tfhe_decrypt_ct_input_size
+//
+// Returns the per-sample input width: 4 bytes (a big-endian uint32
+// pool index, mod kDecryptValidPool).
+func tfhe_decrypt_ct_input_size() C.size_t {
+	return C.size_t(4)
+}
+
+//export tfhe_decrypt_ct
+//
+// One dudect measurement sample. `data` points to a 4-byte
+// big-endian uint32 pool index. We read the index, take its mod
+// against the pool size, and Decrypt the indexed ciphertext.
+//
+// This is CT over `data` beyond the modular reduction.
+func tfhe_decrypt_ct(data *C.uint8_t) {
+	if dFhDecrypt == nil {
+		return
+	}
+	src := unsafe.Slice((*byte)(unsafe.Pointer(data)), 4)
+	idx := (uint32(src[0])<<24 | uint32(src[1])<<16 | uint32(src[2])<<8 | uint32(src[3])) %
+		uint32(kDecryptValidPool)
+	_ = dFhDecrypt.Decrypt(dFhPool[idx])
+}
+
+func main() {}
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2025-2026, Lux Industries Inc. All rights reserved.
+ * See the file LICENSE for licensing terms.
+ *
+ * dudect_bootstrap.c -- dudect main loop driving the TFHE programmable
+ * bootstrap (PBS) through the cgo bridge in bootstrap_ct.go.
+ *
+ * PBS = key_switch o sample_extract o blind_rotate. The composite is
+ * the heaviest TFHE primitive; we use a smaller default measurement
+ * budget than for verify/decrypt.
+ */
+
+#define DUDECT_IMPLEMENTATION
+#include "dudect/src/dudect.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* Exported by libtfhe_bootstrap (bootstrap_ct.go). */
+extern int    tfhe_bootstrap_ct_setup(void);
+extern size_t tfhe_bootstrap_ct_pool_size(void);
+extern size_t tfhe_bootstrap_ct_input_size(void);
+extern void   tfhe_bootstrap_ct(uint8_t *data);
+
+static size_t g_chunk_size = 0;
+static size_t g_pool_size  = 0;
+
+void prepare_inputs(dudect_config_t *cfg, uint8_t *input_data, uint8_t *classes) {
+    for (size_t i = 0; i < cfg->number_measurements; i++) {
+        classes[i] = randombit();
+        uint8_t *slot = input_data + (size_t)i * cfg->chunk_size;
+        if (classes[i] == 0) {
+            slot[0] = 0;
+            slot[1] = 0;
+            slot[2] = 0;
+            slot[3] = 0;
+        } else {
+            uint8_t pick_buf[8];
+            randombytes(pick_buf, sizeof pick_buf);
+            uint64_t pick = 0;
+            for (size_t k = 0; k < sizeof pick_buf; k++) {
+                pick = (pick << 8) | pick_buf[k];
+            }
+            uint32_t idx = (uint32_t)(pick % g_pool_size);
+            slot[0] = (uint8_t)(idx >> 24);
+            slot[1] = (uint8_t)(idx >> 16);
+            slot[2] = (uint8_t)(idx >> 8);
+            slot[3] = (uint8_t)(idx);
+        }
+    }
+}
+
+uint8_t do_one_computation(uint8_t *data) {
+    tfhe_bootstrap_ct(data);
+    uint8_t acc = 0;
+    for (size_t i = 0; i < g_chunk_size; i++) acc ^= data[i];
+    return acc;
+}
+
+int main(int argc, char **argv) {
+    (void)argc;
+    (void)argv;
+
+    int rc = tfhe_bootstrap_ct_setup();
+    if (rc != 0) {
+        fprintf(stderr, "tfhe_bootstrap_ct_setup failed: rc=%d\n", rc);
+        return 1;
+    }
+    g_chunk_size = tfhe_bootstrap_ct_input_size();
+    g_pool_size  = tfhe_bootstrap_ct_pool_size();
+    if (g_chunk_size == 0 || g_pool_size == 0) {
+        fprintf(stderr, "tfhe_bootstrap_ct sizes returned 0\n");
+        return 1;
+    }
+
+    /*
+     * Smaller default budget for PBS (~50-80 ms each on M2 Pro).
+     * Full submission run: DUDECT_SAMPLES=100000 DUDECT_MAX_BATCHES=100.
+     */
+    const char *env_samples = getenv("DUDECT_SAMPLES");
+    const char *env_batches = getenv("DUDECT_MAX_BATCHES");
+    size_t samples = env_samples ? (size_t)atoll(env_samples) : 2000;
+    size_t batches = env_batches ? (size_t)atoll(env_batches) : 50;
+
+    dudect_config_t cfg = {
+        .chunk_size          = g_chunk_size,
+        .number_measurements = samples,
+        .max_number_batches  = batches,
+    };
+    dudect_ctx_t ctx;
+    dudect_init(&ctx, &cfg);
+
+    dudect_state_t state = DUDECT_NO_LEAKAGE_EVIDENCE_YET;
+    while (state == DUDECT_NO_LEAKAGE_EVIDENCE_YET) {
+        state = dudect_main(&ctx);
+    }
+    dudect_free(&ctx);
+
+    if (state == DUDECT_LEAKAGE_FOUND) {
+        fprintf(stderr, "VERDICT: leakage detected in tfhe.Bootstrap\n");
+        return 2;
+    }
+    fprintf(stdout, "VERDICT: no leakage detected within budget\n");
+    return 0;
+}
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2025-2026, Lux Industries Inc. All rights reserved.
+ * See the file LICENSE for licensing terms.
+ *
+ * dudect_compat.h — minimal x86-intrinsic compatibility shim for
+ * AArch64 hosts.
+ *
+ * Upstream dudect.h (https://github.com/oreparaz/dudect) hard-codes
+ * x86 intrinsics for cycle counting:
+ *
+ *   _mm_mfence()  — memory barrier
+ *   __rdtsc()     — read time-stamp counter
+ *
+ * On AArch64 hosts (Apple Silicon, AWS Graviton, etc.), these are
+ * not available. This shim supplies equivalents.
+ *
+ * Counter source by OS:
+ *   - Linux/AArch64: CNTVCT_EL0 — the AArch64 generic timer counter.
+ *     Readable from EL0 on every supported kernel. Monotonic.
+ *     Frequency from CNTFRQ_EL0 (typically 50-100 MHz; the resulting
+ *     resolution is coarser than RDTSC but the t-test is dimensionless
+ *     in counter units so the constant-time verdict is unchanged.)
+ *   - Darwin/AArch64 (Apple Silicon): CNTVCT_EL0 is exposed but reads
+ *     in user mode have been observed to return non-monotonic values
+ *     (the timer is virtualised differently per-process). We use
+ *     mach_absolute_time() instead, which the XNU kernel guarantees is
+ *     monotonic and high-resolution. The tick frequency is exposed via
+ *     mach_timebase_info but we don't normalise — dudect operates on
+ *     raw deltas only.
+ *
+ * The shim is included BEFORE dudect.h via -include, so it intercepts
+ * the x86 headers (<emmintrin.h>, <x86intrin.h>) by providing the
+ * symbols dudect needs without ever pulling in the SSE/AVX
+ * headerset.
+ */
+
+#ifndef DUDECT_COMPAT_H
+#define DUDECT_COMPAT_H
+
+#if defined(__aarch64__)
+
+#include <stdint.h>
+
+/*
+ * Replace x86 intrinsic headers with empty stubs on ARM64 so dudect.h
+ * can include them as written.
+ */
+#define _EMMINTRIN_H_INCLUDED
+#define __EMMINTRIN_H
+#define _IMMINTRIN_H_INCLUDED
+#define _X86INTRIN_H_INCLUDED
+#define __X86INTRIN_H
+
+/*
+ * Full data + instruction barrier. dudect calls this immediately
+ * before reading the cycle counter to keep memory operations ordered
+ * with respect to the counter read.
+ */
+static inline void _mm_mfence(void) {
+    __asm__ __volatile__("dsb sy" ::: "memory");
+}
+
+#if defined(__APPLE__)
+
+#include <mach/mach_time.h>
+
+/*
+ * Apple Silicon: use mach_absolute_time(). High-resolution, monotonic,
+ * kernel-virtualised. Resolution is typically 1 ns (24 MHz timer with
+ * 41.667 ns per tick × scaler — varies by Mac model; XNU normalises
+ * via mach_timebase_info).
+ *
+ * mach_absolute_time() is observably free of the non-monotonic
+ * artefacts CNTVCT_EL0 has in EL0 on macOS.
+ */
+static inline uint64_t __rdtsc(void) {
+    return mach_absolute_time();
+}
+
+#else  /* Linux / *BSD on AArch64 */
+
+/*
+ * Read the AArch64 virtual count register (CNTVCT_EL0). Readable
+ * from EL0 by default on Linux. ISB before the read ensures the
+ * counter read is not speculated past the preceding fence.
+ */
+static inline uint64_t __rdtsc(void) {
+    uint64_t v;
+    __asm__ __volatile__("isb; mrs %0, cntvct_el0" : "=r" (v));
+    return v;
+}
+
+#endif /* __APPLE__ */
+
+#endif /* __aarch64__ */
+
+#endif /* DUDECT_COMPAT_H */
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2025-2026, Lux Industries Inc. All rights reserved.
+ * See the file LICENSE for licensing terms.
+ *
+ * dudect_decrypt.c -- dudect main loop driving fhe.Decryptor.Decrypt
+ * through the cgo bridge in decrypt_ct.go.
+ *
+ * Decrypt is the most CT-critical TFHE routine -- a timing leak
+ * here leaks bits of the secret key. The harness uses a pool of
+ * valid ciphertexts pre-generated under the same secret key, with
+ * varying plaintext bits, so any timing difference is a real
+ * secret-content-dependent signal in Decrypt.
+ */
+
+#define DUDECT_IMPLEMENTATION
+#include "dudect/src/dudect.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* Exported by libtfhe_decrypt (decrypt_ct.go). */
+extern int    tfhe_decrypt_ct_setup(void);
+extern size_t tfhe_decrypt_ct_pool_size(void);
+extern size_t tfhe_decrypt_ct_input_size(void);
+extern void   tfhe_decrypt_ct(uint8_t *data);
+
+static size_t g_chunk_size = 0;
+static size_t g_pool_size  = 0;
+
+void prepare_inputs(dudect_config_t *cfg, uint8_t *input_data, uint8_t *classes) {
+    for (size_t i = 0; i < cfg->number_measurements; i++) {
+        classes[i] = randombit();
+        uint8_t *slot = input_data + (size_t)i * cfg->chunk_size;
+        if (classes[i] == 0) {
+            /* class A: pool[0] every time. */
+            slot[0] = 0;
+            slot[1] = 0;
+            slot[2] = 0;
+            slot[3] = 0;
+        } else {
+            /* class B: uniformly-chosen pool index. */
+            uint8_t pick_buf[8];
+            randombytes(pick_buf, sizeof pick_buf);
+            uint64_t pick = 0;
+            for (size_t k = 0; k < sizeof pick_buf; k++) {
+                pick = (pick << 8) | pick_buf[k];
+            }
+            uint32_t idx = (uint32_t)(pick % g_pool_size);
+            slot[0] = (uint8_t)(idx >> 24);
+            slot[1] = (uint8_t)(idx >> 16);
+            slot[2] = (uint8_t)(idx >> 8);
+            slot[3] = (uint8_t)(idx);
+        }
+    }
+}
+
+uint8_t do_one_computation(uint8_t *data) {
+    tfhe_decrypt_ct(data);
+    uint8_t acc = 0;
+    for (size_t i = 0; i < g_chunk_size; i++) acc ^= data[i];
+    return acc;
+}
+
+int main(int argc, char **argv) {
+    (void)argc;
+    (void)argv;
+
+    int rc = tfhe_decrypt_ct_setup();
+    if (rc != 0) {
+        fprintf(stderr, "tfhe_decrypt_ct_setup failed: rc=%d\n", rc);
+        return 1;
+    }
+    g_chunk_size = tfhe_decrypt_ct_input_size();
+    g_pool_size  = tfhe_decrypt_ct_pool_size();
+    if (g_chunk_size == 0 || g_pool_size == 0) {
+        fprintf(stderr, "tfhe_decrypt_ct sizes returned 0\n");
+        return 1;
+    }
+
+    const char *env_samples = getenv("DUDECT_SAMPLES");
+    const char *env_batches = getenv("DUDECT_MAX_BATCHES");
+    size_t samples = env_samples ? (size_t)atoll(env_samples) : 10000;
+    size_t batches = env_batches ? (size_t)atoll(env_batches) : 100;
+
+    dudect_config_t cfg = {
+        .chunk_size          = g_chunk_size,
+        .number_measurements = samples,
+        .max_number_batches  = batches,
+    };
+    dudect_ctx_t ctx;
+    dudect_init(&ctx, &cfg);
+
+    dudect_state_t state = DUDECT_NO_LEAKAGE_EVIDENCE_YET;
+    while (state == DUDECT_NO_LEAKAGE_EVIDENCE_YET) {
+        state = dudect_main(&ctx);
+    }
+    dudect_free(&ctx);
+
+    if (state == DUDECT_LEAKAGE_FOUND) {
+        fprintf(stderr, "VERDICT: leakage detected in tfhe.Decrypt\n");
+        return 2;
+    }
+    fprintf(stdout, "VERDICT: no leakage detected within budget\n");
+    return 0;
+}
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2025-2026, Lux Industries Inc. All rights reserved.
+ * See the file LICENSE for licensing terms.
+ *
+ * dudect_encrypt.c -- dudect main loop driving fhe.Encryptor.EncryptSafe
+ * through the cgo bridge in encrypt_ct.go.
+ *
+ * dudect API contract: the user provides do_one_computation(data) and
+ * prepare_inputs(cfg, input, classes); dudect's `dudect_main` invokes
+ * them via the extern declarations at the bottom of dudect.h.
+ *
+ * We define DUDECT_IMPLEMENTATION exactly once before including the
+ * header so the whole library compiles into this translation unit.
+ */
+
+#define DUDECT_IMPLEMENTATION
+#include "dudect/src/dudect.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* Exported by libtfhe_encrypt (encrypt_ct.go). */
+extern int    tfhe_encrypt_ct_setup(void);
+extern size_t tfhe_encrypt_ct_input_size(void);
+extern void   tfhe_encrypt_ct(uint8_t *data);
+
+static size_t g_chunk_size = 0;
+
+/*
+ * dudect API hook: populate cfg->number_measurements samples of
+ * cfg->chunk_size bytes each, and assign each sample a binary class
+ * label (0 = fixed class A, 1 = random class B).
+ *
+ * class A: byte 0 = 0  (encrypt false)
+ * class B: byte 0 = uniformly-random byte (encrypt random bit)
+ */
+void prepare_inputs(dudect_config_t *cfg, uint8_t *input_data, uint8_t *classes) {
+    for (size_t i = 0; i < cfg->number_measurements; i++) {
+        classes[i] = randombit();
+        uint8_t *slot = input_data + (size_t)i * cfg->chunk_size;
+        if (classes[i] == 0) {
+            slot[0] = 0;  /* always 0 in class A */
+        } else {
+            uint8_t r;
+            randombytes(&r, 1);
+            slot[0] = r;
+        }
+    }
+}
+
+/*
+ * dudect API hook: one measurement sample. Must depend on `data` so
+ * the compiler cannot dead-code-eliminate the body, must NOT branch
+ * on `data` (or we measure our own branch), and must return a
+ * uint8_t that flows out of the function so the result is observed.
+ */
+uint8_t do_one_computation(uint8_t *data) {
+    tfhe_encrypt_ct(data);
+    uint8_t acc = 0;
+    for (size_t i = 0; i < g_chunk_size; i++) acc ^= data[i];
+    return acc;
+}
+
+int main(int argc, char **argv) {
+    (void)argc;
+    (void)argv;
+
+    int rc = tfhe_encrypt_ct_setup();
+    if (rc != 0) {
+        fprintf(stderr, "tfhe_encrypt_ct_setup failed: rc=%d\n", rc);
+        return 1;
+    }
+    g_chunk_size = tfhe_encrypt_ct_input_size();
+    if (g_chunk_size == 0) {
+        fprintf(stderr, "tfhe_encrypt_ct_input_size returned 0\n");
+        return 1;
+    }
+
+    /*
+     * SMOKE-TEST default (10 000 samples per batch). The full NIST
+     * submission run is 10^9 samples on a quiet, CPU-pinned host;
+     * override via env vars:
+     *   DUDECT_SAMPLES=1000000 DUDECT_MAX_BATCHES=1000 ./dudect_encrypt
+     */
+    const char *env_samples  = getenv("DUDECT_SAMPLES");
+    const char *env_batches  = getenv("DUDECT_MAX_BATCHES");
+    size_t samples = env_samples  ? (size_t)atoll(env_samples)  : 10000;
+    size_t batches = env_batches  ? (size_t)atoll(env_batches)  : 100;
+
+    dudect_config_t cfg = {
+        .chunk_size         = g_chunk_size,
+        .number_measurements = samples,
+        .max_number_batches  = batches,
+    };
+    dudect_ctx_t ctx;
+    dudect_init(&ctx, &cfg);
+
+    dudect_state_t state = DUDECT_NO_LEAKAGE_EVIDENCE_YET;
+    while (state == DUDECT_NO_LEAKAGE_EVIDENCE_YET) {
+        state = dudect_main(&ctx);
+    }
+    dudect_free(&ctx);
+
+    if (state == DUDECT_LEAKAGE_FOUND) {
+        fprintf(stderr, "VERDICT: leakage detected in tfhe.Encrypt\n");
+        return 2;
+    }
+    fprintf(stdout, "VERDICT: no leakage detected within budget\n");
+    return 0;
+}
@@ -0,0 +1,91 @@
+// Copyright (C) 2025-2026, Lux Industries Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+//go:build tfhe_encrypt_ct
+
+// encrypt_ct.go -- cgo bridge exposing TFHE Encrypt to the C dudect
+// harness in dudect_encrypt.c.
+//
+// CT POPULATION (operational framing):
+//   Both dudect classes are VALID Encrypt invocations differing in
+//   the secret bit being encrypted:
+//     class A: always encrypt(false)
+//     class B: encrypt(random bit)
+//   Any timing difference between classes is a real bit-dependent
+//   timing in the Encrypt pipeline.
+//
+// The fixture uses Lux's default parameter set PN10QP27 with a
+// freshly-generated secret key. Each dudect sample re-invokes
+// Encrypt; the leakage profile is the per-call wall-clock + cycle
+// counter as collected by dudect's measurement loop.
+//
+// Build (Linux):
+//   GOWORK=off go build -buildmode=c-shared \
+//       -o libtfhe_encrypt.so ./encrypt_ct.go
+// Build (macOS):
+//   GOWORK=off go build -buildmode=c-shared \
+//       -o libtfhe_encrypt.dylib ./encrypt_ct.go
+
+package main
+
+/*
+#cgo arm64 CFLAGS: -include ${SRCDIR}/dudect_compat.h
+#include <stdint.h>
+#include <stddef.h>
+*/
+import "C"
+
+import (
+	"unsafe"
+
+	"github.com/luxfi/fhe"
+)
+
+// Long-lived fixture.
+var (
+	fhParams  fhe.Parameters
+	fhSecret  *fhe.SecretKey
+	fhEncrypt *fhe.Encryptor
+)
+
+//export tfhe_encrypt_ct_setup
+//
+// Initialise the long-lived fixture. Returns 0 on success.
+func tfhe_encrypt_ct_setup() C.int {
+	params, err := fhe.NewParametersFromLiteral(fhe.PN10QP27)
+	if err != nil {
+		return 1
+	}
+	kg := fhe.NewKeyGenerator(params)
+	sk := kg.GenSecretKey()
+	fhParams = params
+	fhSecret = sk
+	fhEncrypt = fhe.NewEncryptor(params, sk)
+	return 0
+}
+
+//export tfhe_encrypt_ct_input_size
+//
+// Returns the per-sample input width: 1 byte (the bit to encrypt,
+// where any non-zero value is `true`).
+func tfhe_encrypt_ct_input_size() C.size_t {
+	return C.size_t(1)
+}
+
+//export tfhe_encrypt_ct
+//
+// One dudect measurement sample. `data` points to a 1-byte input.
+// data[0] = 0 => encrypt(false); data[0] != 0 => encrypt(true).
+//
+// This call must NOT branch on the input bit beyond the conversion
+// from byte to bool.
+func tfhe_encrypt_ct(data *C.uint8_t) {
+	if fhEncrypt == nil {
+		return
+	}
+	src := unsafe.Slice((*byte)(unsafe.Pointer(data)), 1)
+	bit := src[0] != 0
+	_, _ = fhEncrypt.EncryptSafe(bit)
+}
+
+func main() {}
@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# Fetch dudect at the pinned commit used by Pulsar's constant-time
+# track.
+#
+# dudect (https://github.com/oreparaz/dudect) is a single-header
+# leakage-detection library. We do not vendor dudect.h into this
+# repository — this script reproduces it on demand.
+#
+# Pinned hash at submission-tag time. Update at the same time as the
+# Pulsar submission tag so the artifact chain stays reproducible.
+
+set -euo pipefail
+
+# Repo + commit (master HEAD as of the dudect harness scaffold land).
+# Update when bumping the submission tag.
+DUDECT_REPO="https://github.com/oreparaz/dudect.git"
+DUDECT_COMMIT="master"
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$SCRIPT_DIR"
+
+if [[ -d dudect/.git ]]; then
+    echo "==> dudect already cloned at $SCRIPT_DIR/dudect"
+    ( cd dudect && git fetch --quiet origin && git checkout --quiet "$DUDECT_COMMIT" )
+else
+    echo "==> cloning dudect at $DUDECT_COMMIT"
+    git clone --quiet "$DUDECT_REPO" dudect
+    ( cd dudect && git checkout --quiet "$DUDECT_COMMIT" )
+fi
+
+# The header we link against is dudect/src/dudect.h. Stamp the resolved
+# revision so reviewers can verify the artifact chain.
+RESOLVED_REV="$(cd dudect && git rev-parse HEAD)"
+echo "==> dudect.h ready at $SCRIPT_DIR/dudect/src/dudect.h  (rev $RESOLVED_REV)"