5 files changed, 115 insertions, 14 deletions
diff --git a/src/add_threshold/cipher.c b/src/add_threshold/cipher.c
index 87267fc..230582d 100644
--- a/src/add_threshold/cipher.c
+++ b/src/add_threshold/cipher.c
@@ -25,6 +25,7 @@ where the input block is split into three shares.
 
 #include "cipher.h"
 #include "constants.h"
+#include "random.h"
 #include "tweakey.h"
 
 
@@ -90,13 +91,10 @@ static void _state_init(
     const uint8_t message[BLOCK_BYTES]
 )
 {
-    // To be replaced by real random numbers!!!
-    uint8_t SHARES_0[BLOCK_BYTES] = {
-        0x0f, 0x1e, 0x2d, 0x3c, 0x4b, 0x5a, 0x69, 0x78, 0x87, 0x96, 0xa5, 0xb4, 0xc3, 0xd2, 0xe1, 0xf0
-    };
-    uint8_t SHARES_1[BLOCK_BYTES] = {
-        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
-    };
+    uint8_t SHARES_0[BLOCK_BYTES];
+    uint8_t SHARES_1[BLOCK_BYTES];
+    randombytes(sizeof(SHARES_0), SHARES_0);
+    randombytes(sizeof(SHARES_1), SHARES_1);
 
     memcpy(X, SHARES_0, BLOCK_BYTES);
     memcpy(Y, SHARES_1, BLOCK_BYTES);
diff --git a/src/add_threshold/implem.mk b/src/add_threshold/implem.mk
new file mode 100644
index 0000000..2925287
--- /dev/null
+++ b/src/add_threshold/implem.mk
@@ -0,0 +1,42 @@
+# This file sets some implementation-specific variables and defines
+# build dependencies.
+
+# Filter out tests on tweakey schedule, as the thresholded API differs.
+tests = $(filter-out test-tweakey,$(basename $(wildcard test-*.c)))
+
+# Filter out traces on tweakable block cipher, as intermediate steps
+# differ significantly.
+traces = $(filter-out traces-tbc,$(basename $(wildcard traces-*.c)))
+
+# Don't trigger warnings for "a&b ^ c".
+CFLAGS += -Wno-parentheses
+
+
+# Build dependencies: add random module; remove unused tests/traces.
+
+# Program => additional objects dependencies
+
+$(results_dir)/test-tbc-decrypt $(results_dir)/test-tbc-encrypt:                        \
+$(results_dir)/src/cipher.o $(results_dir)/src/tweakey.o $(results_dir)/src/random.o
+
+$(results_dir)/test-ae-decrypt $(results_dir)/test-ae-encrypt $(results_dir)/test-ae-roundtrip $(results_dir)/traces-ae: \
+$(results_dir)/src/lilliput-$(mode).o $(results_dir)/src/cipher.o                                                        \
+$(results_dir)/src/tweakey.o $(results_dir)/src/random.o
+
+# Object => headers dependencies
+
+$(results_dir)/$(src_dir)/cipher.o: $(src_dir)/cipher.h                 \
+$(src_dir)/tweakey.h $(src_dir)/random.h $(variant_dir)/parameters.h
+
+$(results_dir)/$(src_dir)/lilliput-i.o $(results_dir)/$(src_dir)/lilliput-ii.o: \
+$(src_dir)/lilliput-ae.h $(src_dir)/cipher.h $(src_dir)/constants.h             \
+$(variant_dir)/parameters.h
+
+$(results_dir)/$(src_dir)/tweakey.o: $(src_dir)/tweakey.h               \
+$(src_dir)/constants.h $(src_dir)/random.h $(variant_dir)/parameters.h
+
+$(results_dir)/test/test-tbc-encrypt.o $(results_dir)/test/test-tbc-decrypt.o $(results_dir)/test/traces-tbc.o: \
+$(src_dir)/cipher.h
+
+$(results_dir)/test/test-ae-encrypt.o $(results_dir)/test/test-ae-decrypt.o $(results_dir)/test/test-ae-roundtrip.o $(results_dir)/test/traces-ae.o: \
+$(src_dir)/lilliput-ae.h
diff --git a/src/add_threshold/random.c b/src/add_threshold/random.c
new file mode 100644
index 0000000..1bd9427
--- /dev/null
+++ b/src/add_threshold/random.c
@@ -0,0 +1,34 @@
+/*
+Implementation of the Lilliput-AE tweakable block cipher.
+
+Author: Kévin Le Gouguec, 2019.
+
+For more information, feedback or questions, refer to our website:
+https://paclido.fr/lilliput-ae
+
+To the extent possible under law, the implementer has waived all copyright
+and related or neighboring rights to the source code in this file.
+http://creativecommons.org/publicdomain/zero/1.0/
+
+---
+
+This file provides a system-specific function to generate random bytes.
+*/
+
+/* glibc < 2.25 does not provide getrandom(2): use the system call. */
+
+#define _GNU_SOURCE
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <unistd.h>
+#include <sys/syscall.h>
+
+#include "random.h"
+
+
+void randombytes(size_t nb, uint8_t out[nb])
+{
+    syscall(SYS_getrandom, out, nb, 0);
+}
diff --git a/src/add_threshold/random.h b/src/add_threshold/random.h
new file mode 100644
index 0000000..12cae15
--- /dev/null
+++ b/src/add_threshold/random.h
@@ -0,0 +1,28 @@
+/*
+Implementation of the Lilliput-AE tweakable block cipher.
+
+Author: Kévin Le Gouguec, 2019.
+
+For more information, feedback or questions, refer to our website:
+https://paclido.fr/lilliput-ae
+
+To the extent possible under law, the implementer has waived all copyright
+and related or neighboring rights to the source code in this file.
+http://creativecommons.org/publicdomain/zero/1.0/
+
+---
+
+This file provides an interface to generate random bytes.
+*/
+
+#ifndef RANDOM_H
+#define RANDOM_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+
+void randombytes(size_t nb, uint8_t out[nb]);
+
+
+#endif /* RANDOM_H */
diff --git a/src/add_threshold/tweakey.c b/src/add_threshold/tweakey.c
index f80ea86..097a79a 100644
--- a/src/add_threshold/tweakey.c
+++ b/src/add_threshold/tweakey.c
@@ -24,6 +24,7 @@ tweakey schedule, where the tweak and the key are split into two shares.
 #include <string.h>
 
 #include "constants.h"
+#include "random.h"
 #include "tweakey.h"
 
 
@@ -39,16 +40,14 @@ void tweakey_state_init(
     const uint8_t tweak[TWEAK_BYTES]
 )
 {
-    // To be replaced by real random numbers!!!
-    uint8_t SHARES_0[KEY_BYTES] = {
-        0x0f, 0x1e, 0x2d, 0x3c, 0x4b, 0x5a, 0x69, 0x78, 0x87, 0x96, 0xa5, 0xb4, 0xc3, 0xd2, 0xe1, 0xf0
-    };
+    uint8_t SHARES_0[KEY_BYTES];
+    randombytes(sizeof(SHARES_0), SHARES_0);
 
-    memcpy(TK_Y,             SHARES_0, KEY_BYTES);
-    memcpy(TK_X,             tweak, TWEAK_BYTES);
+    memcpy(TK_Y, SHARES_0, KEY_BYTES);
+    memcpy(TK_X, tweak, TWEAK_BYTES);
 
     for (size_t i=0; i<KEY_BYTES; i++){
-        TK_X[i+TWEAK_BYTES] = key[i] ^ SHARES_0[i] ;
+        TK_X[i+TWEAK_BYTES] = key[i] ^ SHARES_0[i];
     }
 }