NAME

    Filter::Crypto - Create runnable Perl files encrypted with OpenSSL libcrypto

SYNOPSIS

    # Encrypt a Perl script using the crypt_file script. Run it as usual:
    $ crypt_file --in-place hello.pl
    $ hello.pl

    # Create a PAR archive containing an encrypted Perl script. Run it as usual:
    # (This example assumes that you also have PAR installed.)
    $ pp -f Crypto -M Filter::Crypto::Decrypt -o hello hello.pl
    $ hello

    # Display the Filter-Crypto distribution version number:
    use Filter::Crypto;
    print "This is Filter-Crypto $Filter::Crypto::VERSION\n";

DESCRIPTION

    The Filter-Crypto distribution provides the means to convert your Perl files
    into an encrypted, yet still runnable, format to hide the source code from
    casual prying eyes.

    This is achieved using a Perl source code filter. The encrypted files,
    produced using the Filter::Crypto::CryptFile module, automatically have one
    (unencrypted) line added to the start of them that loads the
    Filter::Crypto::Decrypt module. The latter is a Perl source code filter that
    decrypts the remaining (encrypted) part of the Perl file on the fly when it
    is run. See perlfilter if you want to know more about how Perl source code
    filters work.

    These two modules can be built and installed separately, so it is possible
    to set-up two separate Perl installations: one containing the
    Filter::Crypto::CryptFile module to be used for encrypting your Perl files,
    and another containing only the Filter::Crypto::Decrypt module for
    distributing with your encrypted Perl files so that they can be run but not
    easily decrypted. (Well, not very easily, anyway. Please see the WARNING
    below.)

    Encrypted files can also be produced more conveniently using the crypt_file
    script, or (if you also have the PAR module available) using the
    PAR::Filter::Crypto module. The latter can be utilized by the standard PAR
    tools to produce PAR archives in which your Perl files are encrypted. The
    Filter::Crypto::Decrypt module (only) can also be automatically included in
    these PAR archives, so this is perhaps the easiest way to produce
    redistributable, encrypted Perl files.

    The actual encryption and decryption is performed using one of the symmetric
    cipher algorithms provided by the OpenSSL libcrypto library. The EVP library
    high-level interface functions to the various cipher algorithms themselves
    are used so that your choice of algorithm (and also what password or key to
    use) is made simply by answering some questions when building this
    distribution. See the INSTALL file for more details.

WARNING

    Please see the WARNING in the Filter::Crypto manpage regarding the level of
    security provided for your source code by this software.

    Please also note that the LICENCE terms disclaim any express or implied
    warranty and that the author shall not be liable for any direct or indirect
    damages or loss of data arising from the use of this software.

    In short:

    - Other people may be able to unencrypt your encrypted files;

    - You may not be able to unencrypt your own encrypted files.

    Do keep a copy of the configuration options chosen when building these
    modules, and most importantly make sure you KEEP A BACKUP COPY OF YOUR
    ORIGINAL UNENCRYPTED FILES.

COMPATIBILITY

    Before version 2.00 of this distribution, encrypted source code was simply
    the raw output of the chosen encryption algorithm, which is typically
    "binary" data and therefore susceptible to breakage caused by perl reading
    source files in "text" mode, which has become the default on Windows since
    Perl 5.13.11 (specifically, Perl core commit #270ca148cf).

    As of version 2.00 of this distribution, each byte of encrypted source code
    is now output as a pair of hexadecimal digits and therefore no longer
    susceptible to such breakage.

    THIS IS AN INCOMPATIBLE CHANGE. CURRENT VERSIONS OF THESE MODULES WILL NOT
    BE ABLE TO DECRYPT FILES ENCRYPTED WITH VERSIONS OF THESE MODULES PRIOR TO
    VERSION 2.00 OF THIS DISTRIBUTION, EVEN WHEN BUILT WITH THE SAME
    CONFIGURATION OPTIONS. EXISTING ENCRYPTED FILES WILL NEED TO BE
    RE-ENCRYPTED.

INSTALLATION

    See the INSTALL file.

COPYRIGHT

    Copyright (C) 2004-2010, 2012-2015, 2017, 2020, 2021, 2023 Steve Hay. All
    rights reserved.

LICENCE

    This distribution is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself, i.e. under the terms of either the GNU
    General Public License or the Artistic License, as specified in the LICENCE
    file.