Chilkat encryption doesn't work as expected

Question

I was trying to test file encryption using the chilkat functionality. Based on code found on this example page, I replaced the last part with this:

#  Encrypt a string...
#  The input string is 44 ANSI characters (i.e. 44 bytes), so
#  the output should be 48 bytes (a multiple of 16).
#  Because the output is a hex string, it should
#  be 96 characters long (2 chars per byte).


my $input = "sample.pdf";
# create file handle for the pdf file
open my $fh, '<', $input or die $!;
binmode ($fh);

# the output should be sample.pdf.enc.dec
open my $ffh, '>', "$input.enc.dec" or die $!;
binmode $ffh;

my $encStr;
# read 16 bytes at a time
while (read($fh,my $block,16)) {
    # encrypt the 16 bytes block using encryptStringEnc sub provided by chilkat
    $encStr = $crypt->encryptStringENC($block);
    # Now decrypt:
    # decrypt the encrypted block
    my $decStr = $crypt->decryptStringENC($encStr);
    # print it in the sample.pdf.enc.dec file
    print $ffh $decStr;
}
close $fh;
close $ffh;

Disclaimer: I know the CBC mode is not recommended for file encryption because if one block is lost, the other blocks are lost too. The output file is corrupted and when I look with beyond compare at the two files, there are chunks of the file which match and there are chunks of file which doesn't. What am I doing wrong?

Answer 1

You're trying to use character string encryption (encryptStringENC(), decryptStringENC()) for what is, at least partly, a binary file.

This worked for me:

my $input = "sample.pdf";
# create file handle for the pdf file
open my $fh, '<', $input or die $!;
binmode $fh;

# the output should be sample.pdf.enc.dec
open my $ffh, '>', "$input.enc.dec" or die $!;
binmode $ffh;

my $inData = chilkat::CkByteData->new;
my $encData = chilkat::CkByteData->new;
my $outData = chilkat::CkByteData->new;

# read 16 bytes at a time
while ( my $len = read( $fh, my $block, 16 ) ) {

    $inData->clear;
    $inData->append2( $block, $len );

    $crypt->EncryptBytes( $inData, $encData );
    $crypt->DecryptBytes( $encData, $outData );

    print $ffh $outData->getData;
}

close $fh;
close $ffh;

You likely better off perusing the Chilkat site further though, there are sample codes for binary data.