Thank you very much for your interesting blog!

We think about integrating your source code posted inside this blog entry “Reading Password-Protected ZIP Files in Java” into one of our applications intended to be finally used for production scenarios. Could you please let us know if you have any concerns regarding this approach? Please let us know if there are terms of a license or any other restrictions we might be aware of?

Your help is much appreciated!

Kind Regards,

Chris

Congratulations! your program has become a defacto standard to decrypt password-protected zip files.

But my counterparts are expecting me now to send them PKWare encrypted zip files, after an extensive search I could find java programs which uses AES encryption but not PKWare.

I am in gr8 need of ZipEncryptOutputStream :(

Any help ??

case HEADER:
initKeys(password);
for (int i = 0; i = LFH_SIGNATURE.length) {
skipBytes = 2;
state = State.FLAGS;
}
}
break;
}
// intentionally no break

I ‘m try to write simple program for brute-force password in zip in Operating System Subject. First program for thread

I flow this appnote to decrypt header (12 first byte)

http://www.pkware.com/documents/casestudies/APPNOTE.TXT

Header decrypt with no problem. but I ‘m not understand this message

“After the header is decrypted, the last 1 or 2 bytes in Buffer
should be the high-order word/byte of the CRC for the file being
decrypted, stored in Intel low-byte/high-byte order. Versions of
PKZIP prior to 2.0 used a 2 byte CRC check; a 1 byte CRC check is
used on versions after 2.0. This can be used to test if the password
supplied is correct or not.”

I ‘m try to put correct password. But last decrypted header value not match with
CRC Value (14 – 17 byte position).

Here this code. Write in C++

[code]

#include
#include
#include
#include
#include

#include "pthread.h"

unsigned int crc(unsigned int x , unsigned char b)
{
x = x ^ (unsigned long)b;

for(int i=0; i > 1) ^ 0xEDB88320;
else
x = (x >> 1);
}
return x;
}

int main()
{
FILE *fp;
char zip_location[] = "D:\\Zip\\test_pass.zip";
unsigned char password[] = "1234";
unsigned char header_buffer[12];
unsigned char crc_file[25];
unsigned int keys[3];
unsigned int crc_decrypt;

printf("\nFile = %s\n\n",zip_location);

// First Init 96 Bit Internal State
keys[0] = 0x12345678;
keys[1] = 0x23456789;
keys[2] = 0x34567890;

// Step 1 - Initializing the encryption keys
for(int i=0; i > 24));
}

// Step 2 - Decrypting the encryption header
fp = fopen (zip_location,"r+b");
if(fp == NULL)
{
printf("Error! Can't open file\n");
}
else
{
fread(header_buffer,1,12,fp);

// Jump to CRC32 Section
fseek(fp,14,SEEK_SET);
if(fread(crc_file, 1,4,fp))
{
printf("CRC From File = %X %X %X %X \n\n",crc_file[3],crc_file[2],crc_file[1],crc_file[0]);
}
fclose(fp);
}

for(int i=0; i> 8);

keys[0] = crc(keys[0],c);
keys[1] = keys[1] + (keys[0] & 0x000000FF);
keys[1] = keys[1] * 134775813 + 1;
keys[2] = crc(keys[2],keys[1] >> 24);

header_buffer[i] = c;
}

for(int i=0; i<12; i++)
printf("Buffer[%d]\t= \t0x%X\n",i,header_buffer[i]);

getch();

return 0;
}

[/code]

My email : sum.developer [ a+t ] gmail.com