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LibCrypto: Move Curve25519 related code into separate file

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stelar7 2022-04-16 11:33:09 +02:00 committed by Ali Mohammad Pur
parent 6a7d3006d7
commit 9aaeaf8a22
Notes: sideshowbarker 2024-07-17 12:02:22 +09:00 
Author: https://github.com/stelar7
Commit: https://github.com/SerenityOS/serenity/commit/9aaeaf8a22
Pull-request: https://github.com/SerenityOS/serenity/pull/13708
4 changed files with 466 additions and 267 deletions
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1
Userland/Libraries/LibCrypto/CMakeLists.txt
View file

@ -19,6 +19,7 @@ set(SOURCES
Checksum/CRC32.cpp
Cipher/AES.cpp
Cipher/ChaCha20.cpp
Curves/Curve25519.cpp
Curves/SECP256r1.cpp
Curves/X25519.cpp
Curves/X448.cpp

360
Userland/Libraries/LibCrypto/Curves/Curve25519.cpp Normal file
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@ -0,0 +1,360 @@
/*
* Copyright (c) 2022, stelar7 <dudedbz@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Endian.h>
#include <AK/Types.h>
#include <LibCrypto/Curves/Curve25519.h>
namespace Crypto::Curves {
void Curve25519::set(u32* state, u32 value)
{
state[0] = value;
for (auto i = 1; i < WORDS; i++) {
state[i] = 0;
}
}
void Curve25519::modular_square(u32* state, u32 const* value)
{
// Compute R = (A ^ 2) mod p
modular_multiply(state, value, value);
}
void Curve25519::modular_subtract(u32* state, u32 const* first, u32 const* second)
{
// R = (A - B) mod p
i64 temp = -19;
for (auto i = 0; i < WORDS; i++) {
temp += first[i];
temp -= second[i];
state[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Compute R = A + (2^255 - 19) - B
state[7] += 0x80000000;
modular_reduce(state, state);
}
void Curve25519::modular_add(u32* state, u32 const* first, u32 const* second)
{
// R = (A + B) mod p
u64 temp = 0;
for (auto i = 0; i < WORDS; i++) {
temp += first[i];
temp += second[i];
state[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
modular_reduce(state, state);
}
void Curve25519::modular_multiply(u32* state, u32 const* first, u32 const* second)
{
// Compute R = (A * B) mod p
u64 temp = 0;
u64 carry = 0;
u32 output[WORDS * 2];
// Comba's method
for (auto i = 0; i < 16; i++) {
if (i < WORDS) {
for (auto j = 0; j <= i; j++) {
temp += (u64)first[j] * second[i - j];
carry += temp >> 32;
temp &= 0xFFFFFFFF;
}
} else {
for (auto j = i - 7; j < WORDS; j++) {
temp += (u64)first[j] * second[i - j];
carry += temp >> 32;
temp &= 0xFFFFFFFF;
}
}
output[i] = temp & 0xFFFFFFFF;
temp = carry & 0xFFFFFFFF;
carry >>= 32;
}
// Reduce bit 255 (2^255 = 19 mod p)
temp = (output[7] >> 31) * 19;
// Mask the most significant bit
output[7] &= 0x7FFFFFFF;
// Fast modular reduction 1st pass
for (auto i = 0; i < WORDS; i++) {
temp += output[i];
temp += (u64)output[i + 8] * 38;
output[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Reduce bit 256 (2^256 = 38 mod p)
temp *= 38;
// Reduce bit 255 (2^255 = 19 mod p)
temp += (output[7] >> 31) * 19;
// Mask the most significant bit
output[7] &= 0x7FFFFFFF;
// Fast modular reduction 2nd pass
for (auto i = 0; i < WORDS; i++) {
temp += output[i];
output[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
modular_reduce(state, output);
}
void Curve25519::export_state(u32* state, u8* output)
{
for (u32 i = 0; i < WORDS; i++) {
state[i] = AK::convert_between_host_and_little_endian(state[i]);
}
memcpy(output, state, BYTES);
}
void Curve25519::import_state(u32* state, u8 const* data)
{
memcpy(state, data, BYTES);
for (u32 i = 0; i < WORDS; i++) {
state[i] = AK::convert_between_host_and_little_endian(state[i]);
}
}
void Curve25519::modular_subtract_single(u32* r, u32 const* a, u32 b)
{
i64 temp = -19;
temp -= b;
// Compute R = A - 19 - B
for (u32 i = 0; i < 8; i++) {
temp += a[i];
r[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Compute R = A + (2^255 - 19) - B
r[7] += 0x80000000;
modular_reduce(r, r);
}
void Curve25519::modular_add_single(u32* state, u32 const* first, u32 second)
{
u64 temp = second;
// Compute R = A + B
for (u32 i = 0; i < 8; i++) {
temp += first[i];
state[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
modular_reduce(state, state);
}
u32 Curve25519::modular_square_root(u32* r, u32 const* a, u32 const* b)
{
u32 c[8];
u32 u[8];
u32 v[8];
// To compute the square root of (A / B), the first step is to compute the candidate root x = (A / B)^((p+3)/8)
modular_square(v, b);
modular_multiply(v, v, b);
modular_square(v, v);
modular_multiply(v, v, b);
modular_multiply(c, a, v);
modular_square(u, c);
modular_multiply(u, u, c);
modular_square(u, u);
modular_multiply(v, u, c);
to_power_of_2n(u, v, 3);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, c);
to_power_of_2n(u, v, 7);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, c);
to_power_of_2n(u, v, 15);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, c);
to_power_of_2n(u, v, 31);
modular_multiply(v, u, v);
to_power_of_2n(u, v, 62);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, c);
to_power_of_2n(u, v, 125);
modular_multiply(u, u, v);
modular_square(u, u);
modular_square(u, u);
modular_multiply(u, u, c);
// The first candidate root is U = A * B^3 * (A * B^7)^((p - 5) / 8)
modular_multiply(u, u, a);
modular_square(v, b);
modular_multiply(v, v, b);
modular_multiply(u, u, v);
// The second candidate root is V = U * sqrt(-1)
modular_multiply(v, u, SQRT_MINUS_1);
modular_square(c, u);
modular_multiply(c, c, b);
// Check whether B * U^2 = A
u32 first_comparison = compare(c, a);
modular_square(c, v);
modular_multiply(c, c, b);
// Check whether B * V^2 = A
u32 second_comparison = compare(c, a);
// Select the first or the second candidate root
select(r, u, v, first_comparison);
// Return 0 if the square root exists
return first_comparison & second_comparison;
}
u32 Curve25519::compare(u32 const* a, u32 const* b)
{
u32 mask = 0;
for (u32 i = 0; i < 8; i++) {
mask |= a[i] ^ b[i];
}
// Return 0 if A = B, else 1
return ((u32)(mask | (~mask + 1))) >> 31;
}
void Curve25519::modular_reduce(u32* state, u32 const* data)
{
// R = A mod p
u64 temp = 19;
u32 other[WORDS];
for (auto i = 0; i < WORDS; i++) {
temp += data[i];
other[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Compute B = A - (2^255 - 19)
other[7] -= 0x80000000;
u32 mask = (other[7] & 0x80000000) >> 31;
select(state, other, data, mask);
}
void Curve25519::to_power_of_2n(u32* state, u32 const* value, u8 n)
{
// Pre-compute (A ^ 2) mod p
modular_square(state, value);
// Compute R = (A ^ (2^n)) mod p
for (u32 i = 1; i < n; i++) {
modular_square(state, state);
}
}
void Curve25519::select(u32* state, u32 const* a, u32 const* b, u32 condition)
{
// If B < (2^255 - 19) then R = B, else R = A
u32 mask = condition - 1;
for (auto i = 0; i < WORDS; i++) {
state[i] = (a[i] & mask) | (b[i] & ~mask);
}
}
void Curve25519::copy(u32* state, u32 const* value)
{
for (auto i = 0; i < WORDS; i++) {
state[i] = value[i];
}
}
void Curve25519::modular_multiply_inverse(u32* state, u32 const* value)
{
// Compute R = A^-1 mod p
u32 u[WORDS];
u32 v[WORDS];
// Fermat's little theorem
modular_square(u, value);
modular_multiply(u, u, value);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 3);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 7);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 15);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 31);
modular_multiply(v, u, v);
to_power_of_2n(u, v, 62);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 125);
modular_multiply(u, u, v);
modular_square(u, u);
modular_square(u, u);
modular_multiply(u, u, value);
modular_square(u, u);
modular_square(u, u);
modular_multiply(u, u, value);
modular_square(u, u);
modular_multiply(state, u, value);
}
void Curve25519::modular_multiply_single(u32* state, u32 const* first, u32 second)
{
// Compute R = (A * B) mod p
u64 temp = 0;
u32 output[WORDS];
for (auto i = 0; i < WORDS; i++) {
temp += (u64)first[i] * second;
output[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Reduce bit 256 (2^256 = 38 mod p)
temp *= 38;
// Reduce bit 255 (2^255 = 19 mod p)
temp += (output[7] >> 31) * 19;
// Mask the most significant bit
output[7] &= 0x7FFFFFFF;
// Fast modular reduction
for (auto i = 0; i < WORDS; i++) {
temp += output[i];
output[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
modular_reduce(state, output);
}
}

73
Userland/Libraries/LibCrypto/Curves/Curve25519.h Normal file
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@ -0,0 +1,73 @@
/*
* Copyright (c) 2022, stelar7 <dudedbz@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Random.h>
namespace Crypto::Curves {
class Curve25519 {
public:
static constexpr u8 BASE_POINT_L_ORDER[33] {
0xED, 0xD3, 0xF5, 0x5C, 0x1A, 0x63, 0x12, 0x58,
0xD6, 0x9C, 0xF7, 0xA2, 0xDE, 0xF9, 0xDE, 0x14,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10,
0x00
};
static constexpr u32 CURVE_D[8] {
0x135978A3, 0x75EB4DCA, 0x4141D8AB, 0x00700A4D,
0x7779E898, 0x8CC74079, 0x2B6FFE73, 0x52036CEE
};
static constexpr u32 CURVE_D_2[8] {
0x26B2F159, 0xEBD69B94, 0x8283B156, 0x00E0149A,
0xEEF3D130, 0x198E80F2, 0x56DFFCE7, 0x2406D9DC
};
static constexpr u32 ZERO[8] {
0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000
};
static constexpr u32 SQRT_MINUS_1[8] {
0x4A0EA0B0, 0xC4EE1B27, 0xAD2FE478, 0x2F431806,
0x3DFBD7A7, 0x2B4D0099, 0x4FC1DF0B, 0x2B832480
};
static constexpr u8 BARRETT_REDUCTION_QUOTIENT[33] {
0x1B, 0x13, 0x2C, 0x0A, 0xA3, 0xE5, 0x9C, 0xED,
0xA7, 0x29, 0x63, 0x08, 0x5D, 0x21, 0x06, 0x21,
0xEB, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0x0F
};
static constexpr u8 BITS = 255;
static constexpr u8 BYTES = 32;
static constexpr u8 WORDS = 8;
static constexpr u32 A24 = 121666;
static void set(u32* a, u32 b);
static void select(u32* r, u32 const* a, u32 const* b, u32 c);
static void copy(u32* a, u32 const* b);
static void modular_square(u32* r, u32 const* a);
static void modular_subtract(u32* r, u32 const* a, u32 const* b);
static void modular_reduce(u32* r, u32 const* a);
static void modular_add(u32* r, u32 const* a, u32 const* b);
static void modular_multiply(u32* r, u32 const* a, u32 const* b);
static void modular_multiply_inverse(u32* r, u32 const* a);
static void to_power_of_2n(u32* r, u32 const* a, u8 n);
static void export_state(u32* a, u8* data);
static void import_state(u32* a, u8 const* data);
static void modular_subtract_single(u32* r, u32 const* a, u32 b);
static void modular_multiply_single(u32* r, u32 const* a, u32 b);
static void modular_add_single(u32* r, u32 const* a, u32 b);
static u32 modular_square_root(u32* r, u32 const* a, u32 const* b);
static u32 compare(u32 const* a, u32 const* b);
};
}

299
Userland/Libraries/LibCrypto/Curves/X25519.cpp
View file

@ -7,6 +7,7 @@
#include <AK/ByteReader.h>
#include <AK/Endian.h>
#include <AK/Random.h>
#include <LibCrypto/Curves/Curve25519.h>
#include <LibCrypto/Curves/X25519.h>
namespace Crypto::Curves {
@ -16,52 +17,6 @@ static constexpr u8 BYTES = 32;
static constexpr u8 WORDS = 8;
static constexpr u32 A24 = 121666;
static void import_state(u32* state, ReadonlyBytes data)
{
for (auto i = 0; i < WORDS; i++) {
u32 value = ByteReader::load32(data.offset_pointer(sizeof(u32) * i));
state[i] = AK::convert_between_host_and_little_endian(value);
}
}
static ErrorOr<ByteBuffer> export_state(u32* data)
{
auto buffer = TRY(ByteBuffer::create_uninitialized(BYTES));
for (auto i = 0; i < WORDS; i++) {
u32 value = AK::convert_between_host_and_little_endian(data[i]);
ByteReader::store(buffer.offset_pointer(sizeof(u32) * i), value);
}
return buffer;
}
static void select(u32* state, u32* a, u32* b, u32 condition)
{
// If B < (2^255 - 19) then R = B, else R = A
u32 mask = condition - 1;
for (auto i = 0; i < WORDS; i++) {
state[i] = (a[i] & mask) | (b[i] & ~mask);
}
}
static void set(u32* state, u32 value)
{
state[0] = value;
for (auto i = 1; i < WORDS; i++) {
state[i] = 0;
}
}
static void copy(u32* state, u32* value)
{
for (auto i = 0; i < WORDS; i++) {
state[i] = value[i];
}
}
static void conditional_swap(u32* first, u32* second, u32 condition)
{
u32 mask = ~condition + 1;
@ -72,199 +27,6 @@ static void conditional_swap(u32* first, u32* second, u32 condition)
}
}
static void modular_reduce(u32* state, u32* data)
{
// R = A mod p
u64 temp = 19;
u32 other[WORDS];
for (auto i = 0; i < WORDS; i++) {
temp += data[i];
other[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Compute B = A - (2^255 - 19)
other[7] -= 0x80000000;
u32 mask = (other[7] & 0x80000000) >> 31;
select(state, other, data, mask);
}
static void modular_multiply_single(u32* state, u32* first, u32 second)
{
// Compute R = (A * B) mod p
u64 temp = 0;
u32 output[WORDS];
for (auto i = 0; i < WORDS; i++) {
temp += (u64)first[i] * second;
output[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Reduce bit 256 (2^256 = 38 mod p)
temp *= 38;
// Reduce bit 255 (2^255 = 19 mod p)
temp += (output[7] >> 31) * 19;
// Mask the most significant bit
output[7] &= 0x7FFFFFFF;
// Fast modular reduction
for (auto i = 0; i < WORDS; i++) {
temp += output[i];
output[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
modular_reduce(state, output);
}
static void modular_multiply(u32* state, u32* first, u32* second)
{
// Compute R = (A * B) mod p
u64 temp = 0;
u64 carry = 0;
u32 output[WORDS * 2];
// Comba's method
for (auto i = 0; i < 16; i++) {
if (i < WORDS) {
for (auto j = 0; j <= i; j++) {
temp += (u64)first[j] * second[i - j];
carry += temp >> 32;
temp &= 0xFFFFFFFF;
}
} else {
for (auto j = i - 7; j < WORDS; j++) {
temp += (u64)first[j] * second[i - j];
carry += temp >> 32;
temp &= 0xFFFFFFFF;
}
}
output[i] = temp & 0xFFFFFFFF;
temp = carry & 0xFFFFFFFF;
carry >>= 32;
}
// Reduce bit 255 (2^255 = 19 mod p)
temp = (output[7] >> 31) * 19;
// Mask the most significant bit
output[7] &= 0x7FFFFFFF;
// Fast modular reduction 1st pass
for (auto i = 0; i < WORDS; i++) {
temp += output[i];
temp += (u64)output[i + 8] * 38;
output[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Reduce bit 256 (2^256 = 38 mod p)
temp *= 38;
// Reduce bit 255 (2^255 = 19 mod p)
temp += (output[7] >> 31) * 19;
// Mask the most significant bit
output[7] &= 0x7FFFFFFF;
// Fast modular reduction 2nd pass
for (auto i = 0; i < WORDS; i++) {
temp += output[i];
output[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
modular_reduce(state, output);
}
static void modular_square(u32* state, u32* value)
{
// Compute R = (A ^ 2) mod p
modular_multiply(state, value, value);
}
static void modular_add(u32* state, u32* first, u32* second)
{
// R = (A + B) mod p
u64 temp = 0;
for (auto i = 0; i < WORDS; i++) {
temp += first[i];
temp += second[i];
state[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
modular_reduce(state, state);
}
static void modular_subtract(u32* state, u32* first, u32* second)
{
// R = (A - B) mod p
i64 temp = -19;
for (auto i = 0; i < WORDS; i++) {
temp += first[i];
temp -= second[i];
state[i] = temp & 0xFFFFFFFF;
temp >>= 32;
}
// Compute R = A + (2^255 - 19) - B
state[7] += 0x80000000;
modular_reduce(state, state);
}
static void to_power_of_2n(u32* state, u32* value, u8 n)
{
// compute R = (A ^ (2^n)) mod p
modular_square(state, value);
for (auto i = 1; i < n; i++) {
modular_square(state, state);
}
}
static void modular_multiply_inverse(u32* state, u32* value)
{
// Compute R = A^-1 mod p
u32 u[WORDS];
u32 v[WORDS];
// Fermat's little theorem
modular_square(u, value);
modular_multiply(u, u, value);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 3);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 7);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 15);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 31);
modular_multiply(v, u, v);
to_power_of_2n(u, v, 62);
modular_multiply(u, u, v);
modular_square(u, u);
modular_multiply(v, u, value);
to_power_of_2n(u, v, 125);
modular_multiply(u, u, v);
modular_square(u, u);
modular_square(u, u);
modular_multiply(u, u, value);
modular_square(u, u);
modular_square(u, u);
modular_multiply(u, u, value);
modular_square(u, u);
modular_multiply(state, u, value);
}
ErrorOr<ByteBuffer> X25519::generate_private_key()
{
auto buffer = TRY(ByteBuffer::create_uninitialized(BYTES));
@ -291,7 +53,7 @@ ErrorOr<ByteBuffer> X25519::compute_coordinate(ReadonlyBytes input_k, ReadonlyBy
u32 t2[WORDS] {};
// Copy input to internal state
import_state(k, input_k);
Curve25519::import_state(k, input_k.data());
// Set the three least significant bits of the first byte and the most significant bit of the last to zero,
// set the second most significant bit of the last byte to 1
@ -300,18 +62,18 @@ ErrorOr<ByteBuffer> X25519::compute_coordinate(ReadonlyBytes input_k, ReadonlyBy
k[7] |= 0x40000000;
// Copy coordinate to internal state
import_state(u, input_u);
Curve25519::import_state(u, input_u.data());
// mask the most significant bit in the final byte.
u[7] &= 0x7FFFFFFF;
// Implementations MUST accept non-canonical values and process them as
// if they had been reduced modulo the field prime.
modular_reduce(u, u);
Curve25519::modular_reduce(u, u);
set(x1, 1);
set(z1, 0);
copy(x2, u);
set(z2, 1);
Curve25519::set(x1, 1);
Curve25519::set(z1, 0);
Curve25519::copy(x2, u);
Curve25519::set(z2, 1);
// Montgomery ladder
u32 swap = 0;
@ -323,35 +85,38 @@ ErrorOr<ByteBuffer> X25519::compute_coordinate(ReadonlyBytes input_k, ReadonlyBy
swap = b;
modular_add(t1, x2, z2);
modular_subtract(x2, x2, z2);
modular_add(z2, x1, z1);
modular_subtract(x1, x1, z1);
modular_multiply(t1, t1, x1);
modular_multiply(x2, x2, z2);
modular_square(z2, z2);
modular_square(x1, x1);
modular_subtract(t2, z2, x1);
modular_multiply_single(z1, t2, A24);
modular_add(z1, z1, x1);
modular_multiply(z1, z1, t2);
modular_multiply(x1, x1, z2);
modular_subtract(z2, t1, x2);
modular_square(z2, z2);
modular_multiply(z2, z2, u);
modular_add(x2, x2, t1);
modular_square(x2, x2);
Curve25519::modular_add(t1, x2, z2);
Curve25519::modular_subtract(x2, x2, z2);
Curve25519::modular_add(z2, x1, z1);
Curve25519::modular_subtract(x1, x1, z1);
Curve25519::modular_multiply(t1, t1, x1);
Curve25519::modular_multiply(x2, x2, z2);
Curve25519::modular_square(z2, z2);
Curve25519::modular_square(x1, x1);
Curve25519::modular_subtract(t2, z2, x1);
Curve25519::modular_multiply_single(z1, t2, A24);
Curve25519::modular_add(z1, z1, x1);
Curve25519::modular_multiply(z1, z1, t2);
Curve25519::modular_multiply(x1, x1, z2);
Curve25519::modular_subtract(z2, t1, x2);
Curve25519::modular_square(z2, z2);
Curve25519::modular_multiply(z2, z2, u);
Curve25519::modular_add(x2, x2, t1);
Curve25519::modular_square(x2, x2);
}
conditional_swap(x1, x2, swap);
conditional_swap(z1, z2, swap);
// Retrieve affine representation
modular_multiply_inverse(u, z1);
modular_multiply(u, u, x1);
Curve25519::modular_multiply_inverse(u, z1);
Curve25519::modular_multiply(u, u, x1);
// Encode state for export
return export_state(u);
auto buffer = TRY(ByteBuffer::create_uninitialized(BYTES));
Curve25519::export_state(u, buffer.data());
return buffer;
}
ErrorOr<ByteBuffer> X25519::derive_premaster_key(ReadonlyBytes shared_point)