Leahnaya/PKHeX
1
0
Fork 0
mirror of https://github.com/kwsch/PKHeX.git synced 2026-05-13 23:50:25 -05:00
Code Issues Actions Packages Projects Releases Wiki Activity

Reduce allocation on encrypt/decrypt

Browse Source 
Xor no longer allocates
Encrypt no longer allocates byte[0x60]
temp now allocated on stack instead of heap
Pre-size memorystream (prevents 0xF0 allocation)
This commit is contained in:
Kurt 2022-02-27 01:05:11 -08:00
parent ae74ee7931
commit 044dfe46ae
1 changed files with 36 additions and 45 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

81
PKHeX.Core/Saves/Encryption/MemeCrypto/MemeKey.cs
View File

@ -74,17 +74,15 @@ private byte[] GetAesKey(ReadOnlySpan<byte> data)
internal byte[] AesDecrypt(ReadOnlySpan<byte> input)
{
var key = GetAesKey(input);
var data = input[^0x60..].ToArray();
var temp = new byte[0x10];
var data = input[^0x60..];
var curblock = new byte[0x10];
var outdata = new byte[data.Length];
for (var i = 0; i < data.Length / 0x10; i++) // Reverse Phase 2
for (var i = data.Length - 0x10; i >= 0; i -= 0x10) // Reverse Phase 2
{
var ofs = ((data.Length / 0x10) - 1 - i) * 0x10;
Array.Copy(data, ofs, curblock, 0, 0x10);
var temp1 = Xor(temp, curblock);
temp = AesEcbDecrypt(key, temp1);
temp.CopyTo(outdata, ofs);
var slice = data.Slice(i, 0x10);
Xor(curblock, slice, curblock);
curblock = AesEcbDecrypt(key, curblock);
curblock.CopyTo(outdata, i);
}
// At this point we have Phase1(buf) ^ subkey.
@ -94,29 +92,27 @@ internal byte[] AesDecrypt(ReadOnlySpan<byte> input)
// Well, (a ^ a) = 0. so (block first ^ subkey) ^ (block last ^ subkey)
// = block first ^ block last ;)
var last = outdata.AsSpan(((data.Length / 0x10) - 1) * 0x10, 0x10);
last.CopyTo(temp);
temp = Xor(temp, outdata.AsSpan(0, 0x10));
var first = outdata.AsSpan(0, 0x10);
Span<byte> subkey = stackalloc byte[0x10];
GetSubKey(temp, subkey);
for (var i = 0; i < data.Length / 0x10; i++)
Xor(last, first, curblock);
GetSubKey(curblock, subkey);
for (var i = 0; i < data.Length; i += 0x10)
{
var slice = outdata.AsSpan(0x10 * i, 0x10);
slice.CopyTo(curblock);
var temp1 = Xor(curblock, subkey);
temp1.AsSpan(0, 0x10).CopyTo(slice);
var slice = outdata.AsSpan(i, 0x10);
Xor(slice, subkey, slice);
}
// Now we have Phase1Encrypt(buf).
temp.AsSpan().Clear(); // Clear to all zero
for (var i = 0; i < data.Length / 0x10; i++) // Phase 1: CBC Encryption.
curblock.AsSpan().Clear(); // Clear to all zero
Span<byte> temp = stackalloc byte[0x10];
for (var i = 0; i < data.Length; i += 0x10) // Phase 1: CBC Encryption.
{
var slice = outdata.AsSpan(0x10 * i, 0x10);
var slice = outdata.AsSpan(i, 0x10);
slice.CopyTo(curblock);
var temp1 = AesEcbDecrypt(key, curblock);
var temp2 = Xor(temp1, temp);
temp2.CopyTo(slice);
curblock.CopyTo(temp, 0);
Xor(temp1, temp, slice);
curblock.CopyTo(temp);
}
var outbuf = input.ToArray();
@ -131,35 +127,32 @@ internal byte[] AesEncrypt(ReadOnlySpan<byte> input)
{
var key = GetAesKey(input);
var data = input[^0x60..];
var temp = new byte[0x10];
var curblock = new byte[0x10];
var outdata = new byte[data.Length];
for (var i = 0; i < data.Length / 0x10; i++) // Phase 1: CBC Encryption.
for (var i = 0; i < data.Length; i += 0x10) // Phase 1: CBC Encryption.
{
data.Slice(i * 0x10, 0x10).CopyTo(curblock);
var temp1 = Xor(temp, curblock);
temp = AesEcbEncrypt(key, temp1);
temp.CopyTo(outdata, i * 0x10);
var slice = data.Slice(i, 0x10);
Xor(curblock, slice, curblock);
curblock = AesEcbEncrypt(key, curblock);
curblock.CopyTo(outdata, i);
}
// In between - CMAC stuff
var inbet = outdata.AsSpan(0, 0x10);
temp = Xor(temp, inbet);
Xor(curblock, inbet, curblock);
Span<byte> subkey = stackalloc byte[0x10];
GetSubKey(temp, subkey);
GetSubKey(curblock, subkey);
temp.AsSpan().Clear(); // Memcpy from an all-zero buffer
for (var i = 0; i < data.Length / 0x10; i++)
Span<byte> temp = stackalloc byte[0x10];
curblock.AsSpan().Clear(); // Memcpy from an all-zero buffer
for (var i = data.Length - 0x10; i >= 0; i -= 0x10)
{
var ofs = ((data.Length / 0x10) - 1 - i) * 0x10;
var slice = outdata.AsSpan(ofs, 0x10);
slice.CopyTo(curblock);
byte[] temp2 = Xor(curblock, subkey);
byte[] temp3 = AesEcbEncrypt(key, temp2);
byte[] temp4 = Xor(temp3, temp);
temp4.CopyTo(slice);
temp = temp2;
var slice = outdata.AsSpan(i, 0x10);
Xor(slice, subkey, curblock);
byte[] temp1 = AesEcbEncrypt(key, curblock);
Xor(temp1, temp, slice);
curblock.CopyTo(temp);
}
var outbuf = input.ToArray();
@ -182,13 +175,11 @@ private static void GetSubKey(ReadOnlySpan<byte> temp, Span<byte> subkey)
subkey[0xF] ^= 0x87;
}
private static byte[] Xor(byte[] b1, ReadOnlySpan<byte> b2)
private static void Xor(ReadOnlySpan<byte> b1, ReadOnlySpan<byte> b2, Span<byte> x)
{
Debug.Assert(b1.Length == b2.Length);
var x = new byte[b1.Length];
for (var i = 0; i < b1.Length; i++)
x[i] = (byte)(b1[i] ^ b2[i]);
return x;
}
/// <summary>
@ -261,7 +252,7 @@ private byte[] Exponentiate(BigInteger M, BigInteger Power)
// Helper Method to perform AES ECB Encryption
private static byte[] AesEcbEncrypt(byte[] key, byte[] data)
{
using var ms = new MemoryStream();
using var ms = new MemoryStream(data.Length);
using var aes = Aes.Create();
aes.Mode = CipherMode.ECB;
aes.Padding = PaddingMode.None;
@ -276,7 +267,7 @@ private static byte[] AesEcbEncrypt(byte[] key, byte[] data)
// Helper Method to perform AES ECB Decryption
private static byte[] AesEcbDecrypt(byte[] key, byte[] data)
{
using var ms = new MemoryStream();
using var ms = new MemoryStream(data.Length);
using var aes = Aes.Create();
aes.Mode = CipherMode.ECB;
aes.Padding = PaddingMode.None;