From bae46a0de6a8a49f83ac94e70c4d06773c09b36b Mon Sep 17 00:00:00 2001
From: Martin Kromm <martin.kromm@stud.tu-darmstadt.de>
Date: Wed, 25 Sep 2019 10:48:12 +0200
Subject: [PATCH] LowMC Reimplemented the graycode for the lowmc example such
 that the lowmc example can be compiled again.

---
 src/examples/CMakeLists.txt                |  4 +--
 src/examples/lowmc/common/lowmccircuit.cpp | 36 +++++++++++++++++++---
 src/examples/lowmc/common/lowmccircuit.h   |  5 +--
 3 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/src/examples/CMakeLists.txt b/src/examples/CMakeLists.txt
index b2d3aa35..18e17c3e 100644
--- a/src/examples/CMakeLists.txt
+++ b/src/examples/CMakeLists.txt
@@ -3,9 +3,7 @@ add_subdirectory(bench_operations)
 add_subdirectory(euclidean_distance)
 add_subdirectory(float)
 add_subdirectory(innerproduct)
-#currently not supported due to dependency to gpl code
-#TODO make it work again
-#add_subdirectory(lowmc)
+add_subdirectory(lowmc)
 add_subdirectory(millionaire_prob)
 add_subdirectory(min-euclidean-dist)
 add_subdirectory(psi_phasing)
diff --git a/src/examples/lowmc/common/lowmccircuit.cpp b/src/examples/lowmc/common/lowmccircuit.cpp
index eed2a5f8..2eb006a4 100644
--- a/src/examples/lowmc/common/lowmccircuit.cpp
+++ b/src/examples/lowmc/common/lowmccircuit.cpp
@@ -20,7 +20,8 @@
 #include <ENCRYPTO_utils/crypto/crypto.h>
 
 static uint32_t m_nRndCtr;
-static code* m_tGrayCode;
+static uint32_t* m_tGrayCode;
+static uint32_t* m_tGrayCodeIncrement;
 static uint32_t m_nZeroGate;
 
 //sboxes (m), key-length (k), statesize (n), data (d), rounds (r)
@@ -91,8 +92,8 @@ share* BuildLowMCCircuit(share* val, share* key, BooleanCircuit* circ, LowMCPara
 	m_nZeroGate = zerogate;
 
 	//Build the GrayCode for the optimal window-size
-	uint32_t wsize = floor_log2(statesize) - 2;
-	m_tGrayCode = build_code(wsize);
+	m_tGrayCode = BuildGrayCode(statesize);
+	m_tGrayCodeIncrement = BuildGrayCodeIncrement(statesize);
 
 	//copy the input to the current state
 	for (i = 0; i < statesize; i++)
@@ -117,7 +118,8 @@ share* BuildLowMCCircuit(share* val, share* key, BooleanCircuit* circ, LowMCPara
 
 	}
 
-	destroy_code(m_tGrayCode);
+	free(m_tGrayCode);
+	free(m_tGrayCodeIncrement);
 
 #if PRINT_PERFORMANCE_STATS
 	std::cout << "Total Number of Boolean Gates: " << circ->GetNumGates() << std::endl;
@@ -220,7 +222,7 @@ void FourRussiansMatrixMult(std::vector<uint32_t>& state, uint32_t lowmcstatesiz
 
 	for (i = 0, bitctr = 0; i < ceil_divide(lowmcstatesize, wsize); i++) { //for each column-window
 		for (j = 1; j < (1 << wsize); j++) {
-			lut[m_tGrayCode->ord[j]] = circ->PutXORGate(lut[m_tGrayCode->ord[j - 1]], state_pad[i * wsize + m_tGrayCode->inc[j - 1]]);
+			lut[m_tGrayCode[j]] = circ->PutXORGate(lut[m_tGrayCode[j - 1]], state_pad[i * wsize + m_tGrayCodeIncrement[j - 1]]);
 		}
 
 		for (j = 0; j < lowmcstatesize; j++, bitctr += wsize) {
@@ -273,3 +275,27 @@ void CallbackMultiplyAndDestroy4RMatrix(GATE* gate, void* matrix) {
 	//TODO
 }
 
+uint32_t* BuildGrayCode(uint32_t length) {
+	uint32_t* gray_code = (uint32_t*) malloc(sizeof(uint32_t) * length);
+	for(uint32_t i = 0; i < length; ++i) {
+		gray_code[i] = i ^ (i >> 1);
+	}
+	return gray_code;
+}
+
+uint32_t* BuildGrayCodeIncrement(uint32_t length) {
+	uint32_t* gray_code_increment = (uint32_t*) malloc(sizeof(uint32_t) * length);
+	for(uint32_t i = 0; i < length; ++i) {
+		gray_code_increment[i] = 0;
+	}
+	uint32_t length_inc = 2;
+	while(length_inc < length) {
+		uint32_t length_count = length_inc - 1;
+		while(length_count <= length) {
+			(gray_code_increment[length_count])++;
+			length_count += length_inc;
+		}
+		length_inc <<= 1; 
+	}
+	return gray_code_increment;
+}
diff --git a/src/examples/lowmc/common/lowmccircuit.h b/src/examples/lowmc/common/lowmccircuit.h
index b68ca271..ad4eaf76 100644
--- a/src/examples/lowmc/common/lowmccircuit.h
+++ b/src/examples/lowmc/common/lowmccircuit.h
@@ -22,8 +22,6 @@
 #include "../../../abycore/aby/abyparty.h"
 #include <ENCRYPTO_utils/cbitvector.h>
 #include <ENCRYPTO_utils/typedefs.h>
-//TODO make the graycode functionallity work again, the current graycode implementation depends on gpl code
-//#include <ENCRYPTO_utils/graycode.h>
 #include <cassert>
 
 static const BYTE mpccseed[16] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF };
@@ -74,4 +72,7 @@ void CallbackMultiplyAndDestroy4RMatrix(GATE* gate, void* matrix);
 
 void FourRussiansMatrixMult(std::vector<uint32_t>& state, uint32_t lowmcstatesize, BooleanCircuit* circ);
 
+uint32_t* BuildGrayCode(uint32_t length);
+uint32_t* BuildGrayCodeIncrement(uint32_t length);
+
 #endif /* __LOWMCCIRCUIT_H_ */