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LibCrypto: Add UnsignedBigInteger subtraction and comparison

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This commit is contained in:
Itamar 2020-04-08 13:07:47 +03:00 • committed by Andreas Kling
parent 6201f741d4
commit e0cf40518c
3 changed files with 138 additions and 8 deletions
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60
Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
View file

@ -64,11 +64,47 @@ UnsignedBigInteger UnsignedBigInteger::add(const UnsignedBigInteger& other)
return result;
}
UnsignedBigInteger UnsignedBigInteger::sub(const UnsignedBigInteger& other)
{
UnsignedBigInteger result;
if (*this < other) {
dbg() << "WARNING: bigint subtraction creates a negative number!";
return UnsignedBigInteger::create_invalid();
}
u8 borrow = 0;
for (size_t i = 0; i < other.length(); ++i) {
ASSERT(!(borrow == 1 && m_words[i] == 0));
if (m_words[i] - borrow < other.m_words[i]) {
u64 after_borrow = static_cast<u64>(m_words[i] - borrow) + (UINT32_MAX + 1);
result.m_words.append(static_cast<u32>(after_borrow - static_cast<u64>(other.m_words[i])));
borrow = 1;
} else {
result.m_words.append(m_words[i] - borrow - other.m_words[i]);
borrow = 0;
}
}
for (size_t i = other.length(); i < length(); ++i) {
ASSERT(!(borrow == 1 && m_words[i] == 0));
result.m_words.append(m_words[i] - borrow);
borrow = 0;
}
return result;
}
bool UnsignedBigInteger::operator==(const UnsignedBigInteger& other) const
{
if (trimmed_length() != other.trimmed_length()) {
return false;
}
if (is_invalid() != other.is_invalid()) {
return false;
}
for (size_t i = 0; i < trimmed_length(); ++i) {
if (m_words[i] != other.words()[i])
return false;
@ -76,6 +112,23 @@ bool UnsignedBigInteger::operator==(const UnsignedBigInteger& other) const
return true;
}
bool UnsignedBigInteger::operator<(const UnsignedBigInteger& other) const
{
if (trimmed_length() < other.trimmed_length()) {
return true;
}
if (trimmed_length() > other.trimmed_length()) {
return false;
}
size_t length = trimmed_length();
if (length == 0) {
return false;
}
return m_words[length - 1] < other.m_words[length - 1];
}
size_t UnsignedBigInteger::trimmed_length() const
{
size_t num_leading_zeroes = 0;
@ -86,4 +139,11 @@ size_t UnsignedBigInteger::trimmed_length() const
return length() - num_leading_zeroes;
}
UnsignedBigInteger UnsignedBigInteger::create_invalid()
{
UnsignedBigInteger invalid(0);
invalid.invalidate();
return invalid;
}
}

14
Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
View file

@ -35,9 +35,12 @@ public:
UnsignedBigInteger(u32 x) { m_words.append(x); }
UnsignedBigInteger() {}
static UnsignedBigInteger create_invalid();
const AK::Vector<u32>& words() const { return m_words; }
UnsignedBigInteger add(const UnsignedBigInteger& other);
UnsignedBigInteger sub(const UnsignedBigInteger& other);
size_t length() const { return m_words.size(); }
@ -45,15 +48,26 @@ public:
size_t trimmed_length() const;
bool operator==(const UnsignedBigInteger& other) const;
bool operator<(const UnsignedBigInteger& other) const;
void invalidate() { m_is_invalid = true; }
bool is_invalid() const { return m_is_invalid; }
private:
AK::Vector<u32> m_words;
// Used to indicate a negative result, or a result of an invalid operation
bool m_is_invalid { false };
};
}
inline const LogStream& operator<<(const LogStream& stream, const Crypto::UnsignedBigInteger value)
{
if (value.is_invalid()) {
stream << "Invalid BigInt";
return stream;
}
for (int i = value.length() - 1; i >= 0; --i) {
stream << value.words()[i] << "|";
}

72
Userland/test-crypto.cpp
View file

@ -304,6 +304,7 @@ void hmac_sha512_test_process();
void bigint_test_fibo500();
void bigint_addition_edgecases();
void bigint_subtraction();
int aes_cbc_tests()
{
@ -797,21 +798,26 @@ int bigint_tests()
{
bigint_test_fibo500();
bigint_addition_edgecases();
bigint_subtraction();
return 0;
}
Crypto::UnsignedBigInteger bigint_fibonacci(size_t n)
{
Crypto::UnsignedBigInteger num1(0);
Crypto::UnsignedBigInteger num2(1);
for (size_t i = 0; i < n; ++i) {
Crypto::UnsignedBigInteger t = num1.add(num2);
num2 = num1;
num1 = t;
}
return num1;
}
void bigint_test_fibo500()
{
{
I_TEST((BigInteger | Fibonacci500));
Crypto::UnsignedBigInteger num1(0);
Crypto::UnsignedBigInteger num2(1);
for (int i = 0; i < 500; ++i) {
Crypto::UnsignedBigInteger t = num1.add(num2);
num2 = num1;
num1 = t;
}
bool pass = (num1.words() == AK::Vector<u32> { 315178285, 505575602, 1883328078, 125027121, 3649625763, 347570207, 74535262, 3832543808, 2472133297, 1600064941, 65273441 });
bool pass = (bigint_fibonacci(500).words() == AK::Vector<u32> { 315178285, 505575602, 1883328078, 125027121, 3649625763, 347570207, 74535262, 3832543808, 2472133297, 1600064941, 65273441 });
if (pass)
PASS;
@ -838,3 +844,53 @@ void bigint_addition_edgecases()
}
}
}
void bigint_subtraction()
{
{
I_TEST((BigInteger | Simple Subtraction 1));
Crypto::UnsignedBigInteger num1(80);
Crypto::UnsignedBigInteger num2(70);
if (num1.sub(num2) == Crypto::UnsignedBigInteger(10)) {
PASS;
} else {
FAIL(Incorrect Result);
}
}
{
I_TEST((BigInteger | Simple Subtraction 2));
Crypto::UnsignedBigInteger num1(50);
Crypto::UnsignedBigInteger num2(70);
if (num1.sub(num2).is_invalid()) {
PASS;
} else {
FAIL(Incorrect Result);
}
}
{
I_TEST((BigInteger | Subtraction with borrow));
Crypto::UnsignedBigInteger num1(UINT32_MAX);
Crypto::UnsignedBigInteger num2(1);
Crypto::UnsignedBigInteger num3 = num1.add(num2);
Crypto::UnsignedBigInteger result = num3.sub(num2);
if (result == num1) {
PASS;
} else {
FAIL(Incorrect Result);
}
}
{
I_TEST((BigInteger | Subtraction with large numbers));
Crypto::UnsignedBigInteger num1 = bigint_fibonacci(343);
Crypto::UnsignedBigInteger num2 = bigint_fibonacci(218);
Crypto::UnsignedBigInteger result = num1.sub(num2);
if ((result.add(num2) == num1)
&& (result.words() == Vector<u32> { 811430588, 2958904896, 1130908877, 2830569969, 3243275482, 3047460725, 774025231, 7990 })) {
PASS;
} else {
FAIL(Incorrect Result);
}
}
}