4.44 beta

CPP/7zip/Crypto/Zip/ZipCrypto.cpp

@@ -0,0 +1,65 @@
+// Crypto/ZipCrypto.cpp
+
+#include "StdAfx.h"
+
+#include "ZipCipher.h"
+#include "../../../Common/CRC.h"
+
+namespace NCrypto {
+namespace NZip {
+
+static inline UInt32 ZipCRC32(UInt32 c, Byte  b)
+{
+  return CCRC::Table[(c ^ b) & 0xFF] ^ (c >> 8);
+}
+
+void CCipher::UpdateKeys(Byte b)
+{
+  Keys[0] = ZipCRC32(Keys[0], b);
+  Keys[1] += Keys[0] & 0xff;
+  Keys[1] = Keys[1] * 134775813L + 1;
+  Keys[2] = ZipCRC32(Keys[2], (Byte)(Keys[1] >> 24));
+}
+
+void CCipher::SetPassword(const Byte *password, UInt32 passwordLength)
+{
+  Keys[0] = 305419896L;
+  Keys[1] = 591751049L;
+  Keys[2] = 878082192L;
+  for (UInt32 i = 0; i < passwordLength; i++)
+    UpdateKeys(password[i]);
+}
+
+Byte CCipher::DecryptByteSpec()
+{
+  UInt32 temp = Keys[2] | 2;
+  return (Byte)((temp * (temp ^ 1)) >> 8);
+}
+
+Byte CCipher::DecryptByte(Byte encryptedByte)
+{
+  Byte c = (Byte)(encryptedByte ^ DecryptByteSpec());
+  UpdateKeys(c);
+  return c;
+}
+
+Byte CCipher::EncryptByte(Byte b)
+{
+  Byte c = (Byte)(b ^ DecryptByteSpec());
+  UpdateKeys(b);
+  return c;
+}
+
+void CCipher::DecryptHeader(Byte *buffer)
+{
+  for (int i = 0; i < 12; i++)
+    buffer[i] = DecryptByte(buffer[i]);
+}
+
+void CCipher::EncryptHeader(Byte *buffer)
+{
+  for (int i = 0; i < 12; i++)
+    buffer[i] = EncryptByte(buffer[i]);
+}
+
+}}