some final touches, also fixed shiftEncrypt in LNL.h

README.md

@@ -1,9 +1,7 @@
-# About LNL
+## About LNL
 
 **LNL** (short for **long number library**) is a single-file open source C++ library for arithmetics with arbitrary length numbers. It is designed to be simple and easy to use, taking into account possible applications in cryptography and information security. Current version of LNL only supports arbitrary length integers.
 
-**WARNING:** The library is still under development, so be careful!
-
 ## Contents
 
 - [How to install](#how-to-install)
@@ -41,12 +39,12 @@ The whole library is located in the `LNL.h` header. You can find it in the `incl
 ## How to use
 
 ### General info
-This library introduces a new namespace `LNL` (short for long number library). Inside this namespace there is a `LNL::LongInt` class (arbitrary length integer class) and some functions for mathematical operations.
+This library introduces a new namespace `LNL` (short for **long number library**). Inside this namespace there is a `LNL::LongInt` class (arbitrary length integer class) and some functions for mathematical operations.
 
 ### Creating an instance
 It is possible to create a `LNL::LongInt` instance in different ways: with a `short`, `int`, `long`, `long long` or with unsigned equivalents of these types. It is also possible to create an instance with a `std::string`. If you do not pass a value to the constructor then an instance is initialized with 0 by default.
 
-If you try to initialize with a `std::string` which contains non-digit characters (except front "-") then an instance will be initialized with 0 and an error message will be printed.
+If you try to initialize with a `std::string` which contains non-digit characters (except front `-`) then an instance will be initialized with 0 and an error message will be printed.
 
 Here are some examples:
 ```c++
@@ -135,8 +133,6 @@ Using `LNL::div(x,y)` is faster than operators `/` and `%` if you know you need
 
 ### Random numbers
 
-The `LNL::Random()` function is defined for the LongInt class. It generates a random number of indeterminate size and type LongInt.
-
 There are multiple ways to generate random numbers in LNL:
 
 + `LNL::random()` generates a random number of random size (returns `LNL::LongInt`).

include/LNL-unit-tests.h

@@ -572,11 +572,10 @@ void Test::test_shiftEncryption() {
 	for (long long i = 1; i <= tests; i++) {
 		LongInt initial = random();
 		LongInt msg = initial;
-		long long key = std::rand() % 10;
-
+		long long key = std::rand();
 		shiftEncrypt(msg, key);
 		shiftDecrypt(msg, key);
-		verify("shiftEncryption #" + i, initial, msg);
+		verify("shiftEncryption", initial, msg);
 	}
 }
 

include/LNL.h

@@ -161,10 +161,10 @@ class LongInt {
 	bool isMillerRabinPrime() const; // Miller-Rabin primality test
 	factor_t factor() const; // Returns 2 factors of number
 	friend LongInt randomPrime(long long size); // Generates random prime for encryption algorithms
-	friend LongInt modPowTwo(const LongInt& li, const long long pow, const LongInt& modular);
-	friend LongInt modPow(const LongInt& li, LongInt pow, const LongInt& modular);
-	friend void shiftEncrypt(LongInt& li, long long key);
-	friend void shiftDecrypt(LongInt& li, long long key);
+	friend LongInt modPowTwo(const LongInt& li, const long long pow, const LongInt& modular); // Modular exponentiation by 2 to some power
+	friend LongInt modPow(const LongInt& li, LongInt pow, const LongInt& modular); // Modular exponentiation
+	friend void shiftEncrypt(LongInt& li, long long key); // Caesar's cipher encryption
+	friend void shiftDecrypt(LongInt& li, long long key); // Caesar's cipher decryption
 };
 
 std::vector<int> LongInt::primes;
@@ -1167,6 +1167,7 @@ LongInt random() {
 	return randomNumber;
 }
 
+// Generates random LongInt in some range
 LongInt random(const LongInt& left, const LongInt& right) {
 	std::random_device rd;
     std::mt19937 gen(rd());
@@ -1206,6 +1207,7 @@ LongInt random(const LongInt& left, const LongInt& right) {
 	}
 }
 
+// Generates random LongInt number with specified size
 LongInt random(const long long size) {
 	std::random_device rd;
     std::mt19937 gen(rd());
@@ -1225,6 +1227,7 @@ LongInt random(const long long size) {
 	return result;
 }
 
+// Miller-Rabin primality test
 bool LongInt::isMillerRabinPrime() const {
 	fillPrimes();
 
@@ -1289,6 +1292,7 @@ bool LongInt::isMillerRabinPrime() const {
 	return true;
 }
 
+// Returns 2 factors of number
 factor_t LongInt::factor() const {
 	fillPrimes();
 
@@ -1323,9 +1327,7 @@ factor_t LongInt::factor() const {
 	return {1, *this};
 }
 
-/**
- * 
-*/
+// Generates random prime for encryption algorithms
 LongInt randomPrime(long long size) {
 	// generate random number with size
 	LongInt li = random(size);
@@ -1348,6 +1350,7 @@ LongInt randomPrime(long long size) {
 	return li;
 }
 
+// Modular exponentiation by 2 to some power
 LongInt modPowTwo(const LongInt& li, const long long pow, const LongInt& modular) {
 	LongInt result = li % modular;
 
@@ -1358,6 +1361,7 @@ LongInt modPowTwo(const LongInt& li, const long long pow, const LongInt& modular
 	return result;
 }
 
+// Modular exponentiation
 LongInt modPow(const LongInt& li, LongInt pow, const LongInt& modular) {
 	if (li == 0 || modular == 0) {
 		return 0;
@@ -1380,15 +1384,25 @@ LongInt modPow(const LongInt& li, LongInt pow, const LongInt& modular) {
 	return result;
 }
 
+// Caesar's cipher encryption
 void shiftEncrypt(LongInt& li, long long key) {
+	key %= 10;
 	for (long long i = 0; i < li.size(); i++) {
 		li._digits[i] = (li._digits[i] + key) % 10;
+		if (li._digits[i] < 0) {
+			li._digits[i] += 10;
+		}
 	}
 }
 
+// Caesar's cipher decryption
 void shiftDecrypt(LongInt& li, long long key) {
+	key %= 10;
 	for (long long i = 0; i < li.size(); i++) {
-		li._digits[i] = (li._digits[i] - key + 10) % 10;
+		li._digits[i] = (li._digits[i] - key) % 10;
+		if (li._digits[i] < 0) {
+			li._digits[i] += 10;
+		}
 	}
 }
 

source/benchmark.cpp

@@ -18,7 +18,7 @@
 
 int main(int argc, char *argv[]) {
 	auto begin = std::chrono::steady_clock::now();
-	LNL::pow(LNL::LongInt(2), LNL::LongInt(5000));
+	LNL::pow(LNL::LongInt(2), LNL::LongInt(1000));
 	auto end = std::chrono::steady_clock::now();
 	auto elapsedTime = std::chrono::duration_cast<std::chrono::milliseconds>(end - begin);
 	std::cout << elapsedTime.count();